Patent Publication Number: US-2009237788-A1

Title: Optical apparatus and projector

Description:
BACKGROUND 
     1. Technical Field 
     The present invention relates to an optical apparatus and a projector. 
     2. Related Art 
     There has been a projector including a light source apparatus, a light modulator that modulates the light flux emitted from the light source apparatus in accordance with image information to form image light, and a projection optical apparatus that enlarges and projects the image light. 
     In such a projector, polarizing elements are typically disposed on the light flux incident side and the light flux emitting side of the light modulator (liquid crystal panel), each of the polarizing elements transmitting a predetermined linearly polarized light out of the incident light flux and blocking the other part of the light flux (see International Publication WO 01/055778, for example). 
     In the projector described in International Publication WO 01/055778, a reflective polarizing element is used as the polarizing element disposed on the light flux emitting side of the liquid crystal panel (hereinafter referred to as an emitting-side polarizing element) to not only improve the light resistance and heat resistance of the emitting-side polarizing element but also prevent unwanted light flux reflected off the emitting-side polarizing element from being incident on the liquid crystal panel. 
     Specifically, the emitting-side polarizing element includes a triangular cross-sectional prism having a light flux incident-side end surface perpendicular to the optical axis of the incident light flux and an inclined surface inclined to the light flux incident-side end surface, and a reflective polarizing plate provided on the inclined surface of the prism. The unwanted light flux reflected off the reflective polarizing plate is totally reflected off the light flux incident-side end surface of the prism and is not directed toward the liquid crystal panel. 
     In consideration of the handleability in assembling the liquid crystal panel and the emitting-side polarizing element in the projector, the liquid crystal panel is preferably integrated with the emitting-side polarizing element into a single optical apparatus by bonding the liquid crystal panel to the light flux incident-side end surface of the emitting-side polarizing element with an adhesive. 
     Such a configuration, however, is problematic in that the light reflected off the reflective polarizing plate is not totally reflected but emits through the light flux incident-side end surface depending on the refractive index of the adhesive and the light flux having emitted therethrough affects the liquid crystal panel. 
     SUMMARY 
     An advantage of some aspects of the invention is to provide an optical apparatus that can be readily handled and reduced in size, and a projector. 
     An optical apparatus according to a first aspect of the invention includes an optical element disposed on an optical path along which the light flux emitted from a light source travels, and a polarizing element disposed on the light flux emitting-side of the optical element. The polarizing element includes a first prism having a light flux incident-side end surface on which the light flux having emitted from the optical element is incident and an emitting-side inclined surface inclined to the light flux incident-side end surface, and a polarizing element body provided on the emitting-side inclined surface, the polarizing element body transmitting first linearly polarized light out of the light flux having passed through the first prism and reflecting second linearly polarized light polarized perpendicular to the first linearly polarized light toward the first prism. The optical element is integrated with the polarizing element with an interposed adhesive layer formed on the light flux incident-side end surface. The refractive index n0 of the adhesive layer is set to satisfy the following equation (1): 
       1 ≦n 1 /n 0×sin [2φ−arcsin {n0/ n 1×sin(θ−φ)}−2φ]  (1) 
     where n1 represents the refractive index of the first prism, θ represents the angle between the optical axis of the light flux emitted from the light source and the light flux incident on the light flux incident-side end surface, φ represents the angle between a plane orthogonal to the optical axis and the light flux incident-side end surface, and φ represents the angle between the orthogonal plane and the emitting-side inclined surface. 
     In the first aspect of the invention, X, Y and Z axes are defined as follows: The Z axis is the optical axis of the light flux emitted from the light source (Let the +Z axis direction be the direction in which the light flux is directed). The X axis is perpendicular to not only the z axis but also a normal to the light flux incident-side end surface. The Y axis is perpendicular to the X and Z axes. Further, let the +Y axis direction be the direction in which the distance in the Z-axis direction between the light flux incident-side end surface and the emitting-side inclined surface decreases as the coordinate along the +Y axis increases. 
     The angle θ between the optical axis of the light flux emitted from the light source and the light incident on the light flux incident-side end surface, the angle φ between a plane orthogonal to the optical axis and the light flux incident-side end surface, and the angle φ between the orthogonal plane and the emitting-side inclined surface have positive values along the direction in which the +Z-axis is rotated around the X-axis toward the +Y-axis. 
     According to the first aspect of the invention, integrating the optical element with the polarizing element with the interposed adhesive layer formed on the light flux incident-side end surface allows improvement in handleability and reduction in size. 
     Since the refractive index n0 of the adhesive layer is set to satisfy the equation (1), the second linearly polarized light reflected off the polarizing element body is totally reflected off the light flux incident-side end surface and is not directed toward the optical element. The light flux having emitted from the polarizing element will therefore not affect the optical element. 
     In the optical apparatus according to the first aspect of the invention, the polarizing element preferably further includes a second prism having a light flux emitting-side end surface parallel to the light flux incident-side end surface and transmitting the first linearly polarized light having passed through the polarizing element body, and an incident-side inclined surface inclined to the light flux emitting-side end surface and facing the emitting-side inclined surface, and the second prism is preferably integrated with the first prism. 
     According to the configuration described above, the polarizing element includes the second prism having the light flux emitting-side end surface parallel to the light flux incident-side end surface of the first prism. Since the light flux incident-side end surface is parallel to the light flux emitting-side end surface, the first linearly polarized light that emits through the light flux emitting-side end surface can be set to travel in substantially the same direction as that in which the light flux incident on the polarizing element travels. Therefore, when optical components disposed upstream of the optical element in the optical path and optical components disposed downstream of the polarizing element in the optical path are incorporated in the optical apparatus, the optical system can be readily configured. That is, optical components disposed upstream of the optical element in the optical path and optical components disposed downstream of the polarizing element in the optical path can be incorporated in the optical apparatus, whereby the handleability can be further improved. 
     In the optical apparatus according to the first aspect of the invention, the optical element is preferably comprised of a light modulator including a drive substrate and a counter substrate facing each other and liquid crystal molecules encapsulated between the drive substrate and the counter substrate, the light modulator modulating the incident light flux in accordance with image information to form image light. 
     In the configuration described above, since the optical element is comprised of the light modulator, the space between the light modulator and the emitting-side polarizing element can be sealed. No dust will therefore adhere to the light modulator or the emitting-side polarizing element. It is therefore not necessary to attach a dust protective glass on the light flux emitting side of the light modulator, the dust protective glass shifting any dust that has adhered from the focal position to prevent the dust from creating a shadow in the image light. The configuration of the optical apparatus can therefore be simplified and further reduced in size. 
     A projector according to a second aspect of the invention includes a light source apparatus, a light modulator that modulates the light flux emitted from the light source apparatus in accordance with image information to form image light, a projection optical apparatus that enlarges and projects the image light, and the optical apparatus described above. 
     In the second aspect of the invention, the projector including the optical apparatus described above can provide advantageous effects that are same as those provided in the optical apparatus described above. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will now be described with reference to the accompanying drawings, wherein like numbers reference like elements. 
         FIG. 1  schematically shows a general configuration of a projector according to an embodiment of the invention. 
         FIG. 2  is an exploded perspective view schematically showing the configuration of an optical apparatus in the embodiment. 
         FIG. 3  is a schematic view showing the optical paths along which light fluxes travel in an emitting-side polarizing element in the embodiment. 
         FIG. 4  is a schematic view showing the optical path along which second linearly polarized light travels in a first prism in the embodiment. 
         FIG. 5  is a schematic view showing the optical path along which the second linearly polarized light reflected off a polarizing element body travels and impinges on a light flux incident-side end surface in the embodiment. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     An embodiment of the invention will be described below with reference to the drawings. 
     Key Configuration of Projector 
     Main Configuration of Projector 
       FIG. 1  schematically shows a general configuration of a projector  1 . 
     The projector  1  modulates the light flux emitted from a light source in accordance with image information to form image light, and enlarges and projects the image light that has been formed on a screen (not shown). The projector  1  generally includes an optical unit  3 , a projection lens  4  as the projection optical apparatus, and an outer housing  2  that houses the optical unit  3  and the projection lens  4  and forms the exterior, as shown in  FIG. 1 . 
     Although not specifically shown, the space in the outer housing  2  other than the space for the optical unit  3  and the projection lens  4  houses, for example, a cooling unit including a cooling fan that cools the interior of the projector  1 , a power supply that supplies electric power to the components in the projector  1 , and a control unit that controls the operation of the components in the projector  1 . 
     The optical unit  3  forms image light according to image information by optically processing the light flux emitted from a light source apparatus  31  under the control of the control unit described above. The optical unit  3  includes the light source apparatus  31 , an illumination optical apparatus  32 , a color separation optical apparatus  33 , a relay optical apparatus  34 , an optical apparatus  5 , and optical components housing  35  that houses the optical parts  31  to  34  and the optical apparatus  5  in predetermined positions with respect to an illumination optical axis A set in the optical part housing  35 . 
     The light source apparatus  31  includes a light source lamp  311  and a reflector  312 , as shown in  FIG. 1 . In the light source apparatus  31 , the reflector  312  aligns the light fluxes emitted from the light source lamp  311  in a fixed light-emitting direction, and the aligned light fluxes are directed toward the illumination optical apparatus  32 . 
     The illumination optical apparatus  32  includes a first lens array  321 , a second lens array  322 , a polarization conversion element  323 , and a superimposing lens  324 , as shown in  FIG. 1 . The first lens array  321  divides the light flux outputted from the light source apparatus  31  into a plurality of segmented light fluxes and focuses the divided light fluxes in the vicinity of the second lens array  322 . Each of the segmented light fluxes outputted from the second lens array  322  is incident on the polarization conversion element  323  in such a way that the central axis (principal ray) of the segmented light flux is oriented perpendicular to the plane of incidence of the polarization conversion element  323 , where the segmented light fluxes are converted into substantially one type of linearly polarized light fluxes and outputted. The plurality of segmented light fluxes having emitted from the polarization conversion element  323  as linearly polarized light fluxes and passed through the superimposing lens  324  are superimposed on each of three liquid crystal panels  51 , which will be described later, in the optical apparatus  5 . 
     The color separation optical apparatus  33  includes two dichroic mirrors  331 ,  332  and a reflection mirror  333 , as shown in  FIG. 1 , which serve to separate the plurality of segmented light fluxes outputted from the illumination optical apparatus  32  into red (R), green (G), and blue (B) three color light fluxes. 
     The relay optical apparatus  34  includes a light incident-side lens  341 , a relay lens  343 , and reflection mirrors  342 ,  344 , as shown in  FIG. 1 , and serves to guide the color light fluxes separated by the color separation optical apparatus  33 , for example, guide the red light to a liquid crystal panel for red light  51 R, which will be described later, in the optical apparatus  5 . 
     The optical apparatus  5  modulates incident light fluxes in accordance with image information to form image light. The specific configuration of the optical apparatus  5  will be described later. 
     The projection lens  4  is a combination lens obtained by combining a plurality of lenses, and enlarges and projects the image light outputted from the optical apparatus  5  on the screen. 
     Configuration of Optical Apparatus 
       FIG. 2  is an exploded perspective view schematically showing the configuration of the optical apparatus  5 . 
       FIG. 2  shows only the G light portion in the optical apparatus  5 . The R and B light portions are configured in the same manner as the G light portion is. 
     The optical apparatus  5  includes the liquid crystal panels  51  (a liquid crystal panel for red light  51 R, a liquid crystal panel for green light  51 G, and a liquid crystal panel for blue light  51 B) as the light modulators (optical elements), an incident-side polarizing element  52  disposed upstream of each of the liquid crystal panels  51  in the optical path, an emitting-side polarizing element  53  disposed downstream of each of the liquid crystal panels  51  in the optical path, and a cross dichroic prism  54  as a color combining optical apparatus, as shown in  FIG. 1  or  2 . 
     The configuration of each of the optical parts  51  to  54  will be described below sequentially from the one on the light flux incident side. 
     The incident-side polarizing element  52  transmits only linearly polarized light having a polarization direction that is substantially the same as the polarization direction aligned by the polarization conversion element  323 . In the present embodiment, the incident-side polarizing element  52  is comprised of a reflective polarizer, as in the case of a polarizing element body  533 , which will be described later. 
     The liquid crystal panel  51  encapsulates and seals liquid crystal molecules, an electro-optic substance, between a pair of substrates  511  and  512  made of glass or any other suitable material and having a rectangular shape when viewed from above, as shown in  FIG. 2 . The substrate  511 , which is a drive substrate for driving the liquid crystal molecules, includes a plurality of data lines formed in an arrangement in which they are parallel to each other, a plurality of scan lines formed in an arrangement in which they are perpendicular to the plurality of data lines, pixel electrodes formed in a matrix arrangement at the intersections of the scan lines and the data lines, switching devices, such as TFTs (Thin Film Transistors), and a drive unit for driving the switching devices. The substrate  512 , which is a counter substrate facing the substrate  511  and apart therefrom by a predetermined distance, includes a common electrode to which a predetermined voltage Vcom is applied. The substrates  511  and  512  are connected to an FPC cable  513  that serves as a circuit board electrically connected to the control unit and outputting predetermined drive signals to the scan lines, the data lines, the switching devices, the common electrode, and other components. When the control unit inputs the drive signals through the FPC cable  513 , a voltage is applied between a predetermined one of the pixel electrodes and the common electrode, and the orientation of the liquid crystal molecules present between the pixel electrode and the common electrode is controlled. The polarization direction of the polarized light flux having emitted from the incident-side polarizing element  52  is thus modulated. 
     The emitting-side polarizing element  53  does not transmit all the light flux having emitted from the liquid crystal panel  51  but transmits only first linearly polarized light polarized perpendicular to the transmission axis of the incident-side polarizing element  52 . The emitting-side polarizing element  53  includes a first prism  531 , a second prism  532 , and a polarizing element body  533 , as shown in  FIG. 2 . 
     The first prism  531 , which is comprised of a triangular prism having a substantially right-angled triangular cross-sectional shape, has a light flux incident-side end surface  531 A on which the light flux having emitted from the liquid crystal panel  51  is incident and an emitting-side inclined surface  531 B corresponding to the oblique side of the substantially right-angled triangular cross-sectional shape and inclined to the light flux incident-side end surface  531 A. 
     The second prism  532  is comprised of a triangular prism the cross-sectional shape of which is the same as the right-angled triangular cross-sectional shape of the first prism  531 . The second prism  532  has a light flux emitting-side end surface  532 A parallel to the light flux incident-side end surface  531 A of the first prism  531  and transmitting the first linearly polarized light, and an incident-side inclined surface  532 B corresponding to the oblique side of the right-angled triangular cross-sectional shape and facing the emitting-side inclined surface  531 B of the first prism  531 . The refractive index of the second prism  532  is the same as that of the first prism  531 . 
     The polarizing element body  533  is interposed between the emitting-side inclined surface  531 B and the incident-side inclined surface  532 B, and comprised of a reflective polarizer that transmits the first linearly polarized light and reflects second linearly polarized light. In the present embodiment, the polarizing element body  533  has a large number of fine, linear ribs made of aluminum or any other suitable material and parallel to one another on the surface facing the incident-side inclined surface  532 B, although the ribs are not specifically illustrated. The polarizing element body  533  transmits linearly polarized light polarized perpendicular to the direction in which the linear ribs extend (first linearly polarized light) and reflects linearly polarized light polarized parallel to the direction in which the linear ribs extend (second linearly polarized light). 
     The emitting-side polarizing element  53  has a substantially box-like shape when the members  531  to  533  are in contact with each other and hence integrated, as shown in  FIG. 2 . 
     In  FIG. 2 , the emitting-side inclined surface  531 B is inclined so that the second linearly polarized light is reflected off the polarizing element body  533  downward in the figure. The emitting-side inclined surface  531 B may alternatively be inclined in any direction, upward, downward, rightward, or leftward, as long as the reflected light is not directed toward the liquid crystal panel  51 . 
     The optical paths along which the light fluxes travel in the emitting-side polarizing element  53  (the first linearly polarized light and the second linearly polarized light) will be described later. 
     The cross dichroic prism  54  combines the color light fluxes having passed through the emitting-side polarizing elements  53  to form image light (color image). The cross dichroic prism  54  is formed by bonding four right-angled prisms and thus has a substantially square shape when viewed from above. Two dielectric multilayer films are formed along the interfaces between these bonded right-angled prisms. The dielectric multilayer films transmit the G light having emitted from the liquid crystal panel  51 G and passed through the corresponding emitting-side polarizing element  53 , whereas reflecting the R and B light having emitted from the liquid crystal panels  51 R and  51 B and passed through the corresponding emitting-side polarizing elements  53 . The color light fluxes are thus combined to form a color image. 
     The members  51  to  54  described above are then integrated in the following manner: 
     The light flux emitting-side end surface  532 A of the emitting-side polarizing element  53  is bonded to a light flux incident-side end surface  54 A of the cross dichroic prism  54  with an adhesive, and the light flux incident-side end surface  531 A of the emitting-side polarizing element  53  is bonded to the drive substrate  511  for driving the liquid crystal panel  51  with an adhesive  55  (see  FIG. 3 ), which will be described later. Further, the incident-side polarizing element  52  is fixed to the counter substrate  512 , for example, with an adhesive. 
     Optical Paths Along which Light Fluxes Travel in Emitting-Side Polarizing Element 
       FIG. 3  is a schematic view showing the optical paths along which the light fluxes travel in the emitting-side polarizing element  53 . Specifically,  FIG. 3  is a longitudinal cross-sectional view of the emitting-side polarizing element  53 . 
     In  FIG. 3 , X, Y and Z axes are defined as follows: The Z axis is the optical axis of the light flux emitted from the light source (illumination optical axis A) (Let the +Z axis direction be the direction in which the light flux is directed). The X axis is perpendicular to not only the Z axis but also a normal (not shown) to the light flux incident-side end surface  531 A. The Y axis is perpendicular to the Z and X axes. Further, let the +Y axis direction be the direction in which the distance in the Z-axis direction between the light flux incident-side end surface  531 A and the emitting-side inclined surface  531 B decreases as the coordinate along the +Y axis increases (the upward direction in  FIG. 3 ). 
     A light flux L 1  having emitted from the liquid crystal panel  51  (see  FIG. 2 ) passes through the epoxy-based adhesive  55  and impinges on the light flux incident-side end surface  531 A, as shown in  FIG. 3 . The refractive index n0 of the adhesive  55  as an adhesive layer is set to satisfy the following equation (1), 
       1 ≦n 1/ n 0×sin [2φ−arcsin {n0/ n 1×sin(θ−φ)}−2φ]  (1) 
     where n1 represents the refractive index of the first prism  531 ; θ represents the angle between the illumination optical axis A and the light flux L 1 ; φ represents the angle between the orthogonal plane XY and the light flux incident-side end surface  531 A; and φ represents the angle between the orthogonal plane XY and the emitting-side inclined surface  531 B. The angles θ, φ, and φ have positive values along the direction in which the +Z-axis is rotated around the X-axis toward the +Y-axis (counterclockwise direction in  FIG. 3 ). The same argument applies to the angles described in the following sections. 
     For example, when the first prism  531  is made of a typical optical glass material BK7, the refractive index n1 of BK7 is 1.518. When θ=15 (°), φ=40 ( ), and φ=0 (°), the refractive index n0 of the adhesive  55  determined by the equation (1) satisfies n0≦1.43. 
     That is, SiO 2  having a refractive index of 1.40, MgF 2  having a refractive index of 1.39, or CaF 2  having a refractive index of 1.30 can be used as the adhesive  55  in this example. 
     The optical paths along which the light fluxes travel in the emitting-side polarizing element  53  and the derivation of the equation (1) will be described below. 
     First, the angle θ2 between the illumination optical axis A and a light flux L 2  having passed through the light flux incident-side end surface  531 A is determined by the following equation (2) based on Snell&#39;s law: 
       sin(θ−φ)/sin(θ2−φ)= n 1/ n 0  (2) 
     The light flux L 2  traveling through the first prism  531  is separated into first linearly polarized light L 21  and second linearly polarized light L 22  at the polarizing element body  533 . 
     The first linearly polarized light L 21  passes through the polarizing element body  533 , passes through the second prism  532 , emits through the light flux emitting-side end surface  532 A, and enters the cross dichroic prism  54  (see  FIG. 2 ). The adhesive (not shown) that bonds the light flux emitting-side end surface  532 A to the light flux incident-side end surface  54 A of the cross dichroic prism  54  has the same refractive index n0 as that of the adhesive  55 . The first linearly polarized light L 21  having emitted through the light flux emitting-side end surface  532 A therefore travels in substantially the same direction as the direction in which the light flux L 1  travels. 
       FIG. 4  is a schematic view showing the optical path along which the second linearly polarized light L 22  travels in the first prism  531 . In  FIG. 4 , the second prism  532  is not illustrated. 
     The second linearly polarized light L 22  is reflected off the polarizing element body  533  toward the light flux incident-side end surface  531 A, as shown in  FIG. 4 . 
     The angle θ3 between the illumination optical axis A and the second linearly polarized light L 22  reflected off the polarizing element body  533  toward the light flux incident-side end surface  531 A is determined by the following equation (3): 
       θ3=2φ−θ2  (3) 
       FIG. 5  is a schematic view showing the optical path along which the second linearly polarized light L 22  reflected off the polarizing element body  533  travels and impinges on the light flux incident-side end surface  531 A. In  FIG. 5 , the second prism  532  is not illustrated. 
     The second linearly polarized light L 22  reflected off the polarizing element body  533  is incident on the light flux incident-side end surface  531 A, as shown in  FIG. 5 . 
     Since the angle between the illumination optical axis A and the second linearly polarized light L 22  is the angle θ3 determined by the equation (3), the second linearly polarized light L 22  will be totally reflected off the light flux incident-side end surface  531 A under the condition determined by the following equation (4) based on Snell&#39;s law: 
       1/sin(θ3−φ)≦ n 1/ n 0  (4) 
     The equation (1) described above can be derived by deleting the angles θ2 and θ3 from the equations (2) to (4) and organizing the resultant equation. 
     As described above, since the refractive index n0 of the adhesive  55  is set to satisfy the equation (1), the second linearly polarized light L 22  reflected off the polarizing element body  533  is totally reflected off the light flux incident-side end surface  531 A and is not directed toward the liquid crystal panel  51 . 
     The present embodiment described above provides the following advantages: 
     (1) Integrating the liquid crystal panel  51  with the emitting-side polarizing element  53  with the adhesive  55  therebetween allows improvement in handleability and reduction in size. 
     (2) Since the refractive index n0 of the adhesive  55  is set to satisfy the equation (1), the second linearly polarized light L 22  reflected off the polarizing element body  533  is totally reflected off the light flux incident-side end surface  531 A and is not directed toward the liquid crystal panel  51 . The light flux having emitted from the emitting-side polarizing element  53  will therefore not affect the liquid crystal panel  51 . 
     (3) Since the liquid crystal panel  51  is bonded to the emitting-side polarizing element  53  with the adhesive  55  therebetween so that the space between the two members is sealed, no dust will adhere to the liquid crystal panel  51  or the emitting-side polarizing element  53 . It is therefore not necessary to attach a dust protective glass on the light flux emitting side of the liquid crystal panel, the dust protective glass shifting any dust that has adhered from the focal position to prevent the dust from creating a shadow in the image light. The configuration of the optical apparatus  5  can therefore be simplified and further reduced in size. 
     (4) Since the emitting-side polarizing element  53  includes the second prism  532  having the light flux emitting-side end surface  532 A parallel to the light flux incident-side end surface  531 A of the first prism  531 , the first linearly polarized light L 21  that emits through the light flux emitting-side end surface  532 A can be set to travel in substantially the same direction as that in which the light flux L 1  incident on the emitting-side polarizing element  53  travels. Therefore, the incident-side polarizing element  52  disposed upstream of the liquid crystal panel  51  in the optical path and the cross dichroic prism  54  disposed downstream of the emitting-side polarizing element  53  in the optical path can also be incorporated in the optical apparatus  5 , whereby the handleability can be further improved. 
     Variations 
     The invention is not limited to the embodiment described above, but variations and modifications thereof are encompassed in the invention to the extent that they can achieve the advantage of some aspects of the invention. 
     While in the above embodiment, the epoxy-based adhesive  55  is used as the adhesive layer, the adhesive layer is not limited thereto. For example, a layer made of any of a fluorine-based coating agent, a silicon resin coating agent, and a metal oxide, such as SiO 2  or MgF 2 , may be formed on the light flux incident-side end surface of the polarizing element, and the optical element and the polarizing element are bonded to each other, for example, by pressing them against each other. In essence, the optical element and the polarizing element only needs to be integrated with each other with the interposed adhesive layer formed on the light flux incident-side end surface. 
     While in the above embodiment, the optical parts  51  to  54  are integrated to form the optical apparatus  5 , the configuration of the optical apparatus  5  is not limited thereto. At least the liquid crystal panel  51  should be integrated with the emitting-side polarizing element  53 , but the other optical parts  52  and  54  may not be integrated. 
     While the above embodiment has been described with reference to the emitting-side polarizing element  53  as the polarizing element, the incident-side polarizing element  52  may also be configured in the same manner as the emitting-side polarizing element  53  is, and the optical element disposed upstream of the incident-side polarizing element  52  in the optical path may be integrated therewith. 
     While in the above embodiment, the liquid crystal panel  51  is used as the optical element, the optical element is not limited thereto. The optical element may alternatively be a retardation film, a viewing angle compensator (a WV film (manufactured by FUJIFILM Corporation) or any other suitable optical compensation film attached to a light-transmissive substrate), a light-transmissive substrate made of quartz, sapphire, or any other suitable material having a relatively high thermal conductivity, or other optical elements. 
     While in the above embodiment, the emitting-side polarizing element  53  includes not only the first prism  531  and the polarizing element body  533  but also the second prism  532 , the configuration of the emitting-side polarizing element  53  is not limited thereto. The emitting-side polarizing element  53  may be configured without the second prism  532 . 
     While in the above embodiment, the first prism  531  and the second prism  532  have substantially the same shape and the same refractive index, the first prism  531  and the second prism  532  are not necessarily configured as described above, but may alternatively differ from each other in terms of shape and refractive index. 
     In the above embodiment, the polarizing element body  533  is not necessarily configured as described above, but may be configured in any manner as long as it serves as a reflective polarizer. 
     For example, the polarizing element body  533  may be a polarization separation element formed of a dielectric multilayer film; a polymer-based laminar polarizing plate obtained by stacking organic material layers, each of which having refractive index anisotropy (birefringence), such as liquid crystal materials; an optical element obtained by combining a circularly polarized light reflector that separates unpolarized light into right-handed circularly polarized light and left-handed circularly polarized light with a quarter wave plate; a Brewster angle optical element that separates light into reflected polarized light and transmitted polarized light; or a hologram optical element using a hologram. 
     While the above embodiment has been described only with reference to a front-projection projector, the invention is also applicable to a rear-type projector that includes a screen and projects an image from the backside of the screen. 
     The invention, which allows improvement in handleability and reduction in size, is applicable to a projector used for presentation and in a home theater. 
     The entire disclosure of Japanese Patent Application No. 2008-071997, filed Mar. 19, 2008 and the entire disclosure of Japanese Patent Application No. 2009-008650, filed Jan. 19, 2009 are expressly incorporated by reference herein.