CA2032680C - Image display apparatus - Google Patents
Image display apparatusInfo
- Publication number
- CA2032680C CA2032680C CA 2032680 CA2032680A CA2032680C CA 2032680 C CA2032680 C CA 2032680C CA 2032680 CA2032680 CA 2032680 CA 2032680 A CA2032680 A CA 2032680A CA 2032680 C CA2032680 C CA 2032680C
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- Prior art keywords
- polarized
- radiation source
- polarization
- plane
- optical system
- Prior art date
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Abstract
An image display apparatus has a radiation source, generator for generating an image by modulating a polarized light beam and directing device for directing a light beam from the radiation source toward the generator. The directing device has a conversion optical system for converting the beam from the radiation source into the polarized light beam. The conversion optical system has a polarizing beam splitter for splitting the beam from the radiation source into a first and second beams.
In the conversion optical system, a 1/4 wavelength plate and a mirror are arranged so that the plane of polarization of the first beam is rotated to generate a third beam with the plane of polarization same as that of the second beam. The third beam is directed toward the generator through the polarizing beam splitter while the second beam is also directed toward the generator.
In the conversion optical system, a 1/4 wavelength plate and a mirror are arranged so that the plane of polarization of the first beam is rotated to generate a third beam with the plane of polarization same as that of the second beam. The third beam is directed toward the generator through the polarizing beam splitter while the second beam is also directed toward the generator.
Description
20326~0 The present invention relates to an image display apparatus.
An object of the present invention is to provide an image display apparatus equipped with an improved polarized illuminating device capable of reducing the loss in the amount of light.
The above-mentioned object can be attained, according to a first embodiment of the present invention, by an image display apparatus comprising:
a radiation source;
a generator for generating an image by modulating a polarized light beam; and directing means for directing a light beam from said radiation source toward said generator;
wherein said directing means has a conversion optical system for converting the beam from said radiation source into said polarized light beam;
said conversion optical system comprises a polarizing beam splitter for splitting the beam from said radiation source into a first beam and a second beam whose polarization planes are orthogonal to each other;
and an arrangement of a 1/4 wavelength plate and a mirror for rotating the polarization plane of said first beam to generate a third beam whose polarization plane is same as that of the second beam;
whereby said third beam is directed toward said generator through said polarizing beam splitter 203268~
..~
1 while said second beam is also directed toward said generator.
Also the above-mentioned object can be attained, according to a second embodiment of the present invention, by an image display apparatus comprising:
a radiation source;
a generator for generating an image by modulating a polarized light beam; and directing means for directing a light beam from said radiation source toward said generator;
wherein said directing means comprises a collimator for substantially collimating the beam from ~said radiation source and a conversion optical system for converting thus collimated beam into said polarized beam; and said conversion optical system comprises a polarizing beam splitter with a splitting plane inclined to the optical axis of said collimator, for splitting said collimated beam by transmitting a P-polarized beam thereof while reflecting an S-polarized beam thereof; an arrangement of a 1/4 wavelength plate and a mirror for rotating the polarization plane of said S-polarized beam to generate a polarized beam with a polarized plane coinciding with that of said P-polarized beam and directing said generated polarized beam toward a predetermined direction through said 3 203268d 1 polarizing beam splitter; and an auxiliary mirror for reflectively deflecting said P-polarized beam toward said predetermined direction.
Also the above-mentioned object can be attained, according to a third embodiment of the present invention, by an image display apparatus comprising:
a radiation source;
a generator for generating an image by 0 modulating a polarized light beam; and directing means for directing a light beam from said radiation source toward said generator;
wherein said directing means comprises a collimator for substantially collimating the beam from said radiation source and a conversion optical system for converting thus collimated beam into said polarized beam; and said conversion optical system comprises a first polarizing beam splitter with a splitting plane inclined to the optical axis of said collimator, for splitting said collimated beam by transmitting a P-polarized beam thereof while reflecting an S-polarized beam thereof in a predetermined direction; a second polarizing beam~splitter with a splitting plane inclined to the optical axis of said collimator; and an arrangement of a 1/4 wavelength plate and a mirror for receiving said P-polarized beam through said 2032~8~
1 second polarizing beam splitter, rotating the polarization plane of said P-polarized beam to generate a polarized beam with a polarization plane coinciding with that of said S-polarized beam and reflectively deflecting said generated polarized beam into said predetermined direction through said second polarizing beam splitter.
Also the above-mentioned object can be attained, according to a fourth embodiment of the present invention, by an image display apparatus comprising:
a radiation source;
a generator for generating an image by modulating a polarized light beam; and directing means for directing a light beam from said radiation source toward said generator;
wherein said directing means comprises a collimator for substantially collimating the beam from said radiation source and a conversion optical system for converting thus collimated beam into said polarized beam; and said conversion optical system comprises a polarizing beam splitter with a splitting plane inclined to the optical axis of said~collimator, for splitting said collimated beam by transmitting a P-polarized beam thereof into a predetermined direction while reflecting an S-polarized beam thereof; an 203~0 arrangement of a 1/4 wavelength plate and a mirror for rotating the polarization plane of said S-polarized beam to generate a polarized beam with a polarization plane coinciding with that of said P-polarized beam and directing said generated polarized beam toward said polarizing beam splitter; and an auxiliary mirror for receiving said polarized beam through said polarizing beam splitter and reflectively deflecting said polarized beam into said predetermined direction.
Fig. 1 is a schematic view showing the structure of an example of the conventional projection display apparatus;
Fig. 2 is a schematic view showing the structure of another example of the conventional projection display apparatus;
Fig. 3 is a schematic view showing the structure of a projection display apparatus disclosed in the Japanese Patent Application Laid-Open No. 61-90584;
Fig. 4 is a schematic view showing a drawback encountered when the parallel illumination method is employed in the projection display apparatus shown in Fig. 3;
Fig. 5 is a view of a first embodiment of the polarized illuminating apparatus of the present 6 20326~0 L invention;
Fig. 6 is a schematic view showing the optical path in the polarized illuminating apparatus shown in Fig. 5;
Fig. 7 is a view of a second embodiment of the polarized illuminating apparatus of the present invention;
Fig. 8 is a view of a third embodiment of the polarized illuminating apparatus of the present invention;
Fig. 9 is a view of a fourth embodiment of the polarized illuminating apparatus of the present invention;
. Fig. 10 is a partial view of an embodiment of lS a projection display apparatus provided with the polarized illuminating apparatus shown in Fig. 9; and ~ Figs. llA and llB are respectively a lateral view and a plan view of an embodiment of a projection display apparatus provided with the polarized illuminating apparatus shown in Fig. 5.
Fig. 1 is a schematic view showing the principal structure of an example of the conventional image display apparatus.
Said display apparatus is provided with a light source 1 composed for example of a halogen lamp or a metal halide lamp; a mirror 2 reflecting a part of the light emitted by said light source l; a heat ray cut-off filter 3 for absorbing or reflecting the heat ray in the light entering directly from the light source 1 or indirect~y from the mirror 2; a condenser lens 4 for converting the light, after removal of the heat ray, into a parallel beam; a polarizer 5 for converting said parallel light beam into linearly polarized light; a liquid crystal light valve 7 for modulating said linearly polarized light according to an image signal; a polarizer 8 for transmitting only a component, parallel to the transmission axis thereof, Of said modulated linearly polarized light; and a projection lens lO for projecting the linearly polarized light, transmitted by said polarizer 8, in 20~2gg~
l a magnified scale onto an unrepresented screen.
Fig. 2 is a schematic view showing the principal part of another example of such conventional projection display apparatus.
Said apparatus is equipped with two polarizing beam splitters 6, 9 respectively in front of and behind the light crystal light valve 7, in place for the two polarizers 5, 8 in the apparatus shown in Fig.
1.
The projection display apparatus shown in Figs. 1 and 2 are associated with a drawback that the efficiency of ulitization of light does not exceed 50 %, since, within the light emitted by the light ~source 1, a linearly polarized component transmitted by the polarizing beam splitter 6 alone is utilized for illuminating the light crystal light valve 7 while the perpendicularly polarized component is lost.
Fig. 3 shows a projection display apparatus disclosed in the Japanese Patent Application Laid-Open No. 61-90584 for rectifying said drawback.
In said projection display apparatus the parallel light beam emerging from the condenser lens 4 enters a polarizing beam splitter 11, and the P-polarized component Lp is transmitted by the functional plane (an evaporated film formed on a diagonal plane between two rectangular prisms) lla of said polarizing beam splitter 11, while the -1 S-polarized component Ls is perpendicularly reflected to enter a total reflection prism 12. Being perpendicularly reflected again in said prism 12, the S-polarized component Ls emerges from said prism 12 in a direction same as that of the P-polarized component Lp. The S-polarized component Ls is polarized in a direction parallel to the functional plane lla of the polarizing beam splitter 11, and the P-polarized component Lp is polarized in a direction perpendicular to that of the S-polarized component.
At the exit side of the total reflection 12 there is provided a ~/2-phase shifting plate 13, whereby said S-polarized component L2 is subjected to ~ rotation of the polarizing direction by 90- and is converted into a P-polarized component Lp*. Also at the exit side of the polarizing beam splitter 11 and the A/2-phase shifting plate 13 there are respectively provided wedge-shaped lenses 14, 15 for light path deflection, whereby the P-polarized component Lp transmitted by said polarizing beam splitter 11 and the P-polarized component Lp*
converted by the ~/2-phase shifting plate 13 are subjected to light path deflection and mutually cross at a point P0 on the entrance face of the liquid crystal light valve 7, thereby providing a synthesized light.
Consequently such projection display apparatus 1 can illuminate the liquid crystal light valve 7 with both the S-polarized component Ls and the P-polarized component Lp separated by the polarizing beam splitter 11 and can therefore double the efficiency of light utilization in comparison with the apparatus shown in Fig. 2.
However, in the projection display apparatus disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 61-90584, since the P-polarized component Lp and the P-polarized component Lp* converted by the ~/2-phase shifting plate 13 respectively enter the liquid crystal light valve with an angle 6 as shown in Fig. 3, it is necessary to ~select a considerably large distance from the wedge-shaped lenses 14, 15 to the liquid crystal light valve7 in order to reduce said incident angle e if the light valve 7 shows significant deterioration of characteristics depending on the incident angle.
For avoiding such drawback, there is conceived a parallel illuminating method in which the wedge-shaped lenses 14, 15 shown in Fig. 3 are removed, whereby said P-polarized component Lp and said converted P-polarized component Lp* enter the liquid crystal light valve 7 in mutually parallel state.
However, such parallel illumination method, if applied to the projection display apparatus disclosed in the Japanese Patent Application Laid-Open No. 61-90584, 1 cannot provide the expected result because the P-polarized component Lp and the converted P-polarized component Lp* are not complete unless the light source 1 is a complete point or linear source providing completely parallel beams from the condenser lens 4.
This will be explained further with reference to Fig.
4.
In case the light from a light source 1 with a finite diameter ~ is condensed by a condenser lens 4 at a distance ~, the light emerging therefrom is not completely parallel but is spread within an angular range 2 ~( ~ctan 1 (~ /2)/ ~). A ray a contained in thus obtain non-parallel beam enters the A/2-phase ~shifting plate 13 without the function of the lS polarizing beam splitter 11 and emerges from said phase shifting plate 13 with the P- and S-polarized components. Also a ray ~ is converted by the polarizing beam splitter 11 into the S-polarized component Ls, which is then reflected by the total reflection prism 12 and reflected again by the polarizing beam splitter 11. It thus emerges as a P-polarized component Lp* from another position of the /2-phase shifting plate 13 as indicated by a ray ~1' or is lost by absorpt,on or transmission at the surface of the phase shifting plate 13 as indicated by a ray ~2-203~6~
Now the present invention will be clarified in greater detail by embodiments thereof shown in the attached drawings.
Fig. 5 is a schematic view of a first embodiment of the polarized illuminating apparatus of the present invention, and Fig. 6 is a view showing the optical path thereof.
Said polarized illuminating apparatus is composed of a polarizing beam splitter 26 having a function plane (an evaporated film formed on a diagonal plane at which two rectangular prisms are mutually adhered) for transmitting the P-polarized component Lp of a parallel light beam emerging from a condenser lens 4 while rectangularly reflecting the S-polarized component Ls; a total reflection prism 29 provided with a total reflection plane 29a contacting at an end thereof rectangularly with an end of the functional plane 26a of said polarizing beam 20326~
1 splitter 26 and serving to rectangularly reflect said transmitted P-polarized component Lp; a ~/4 phase shifting plate 27 contacting at an end thereof, at an angle of 45, with an end of the functional plane 26a of said polarizing beam splitter and with an end of the total reflection plane 29a of said total reflection prism 29, and adapted to receive said reflected S-polarized component Ls; and a reflecting plate 28 having a reflecting plane, composed of an aluminum evaporated film or an optical multi-layered film, adhered to said ~/4 phase shifting plate 27.
In said polarized illuminating apparatus, the parallel light beam emerging from the condenser lens 4 'is split into the P-polarized component Lp and the S-polarized component Ls, by respective transmission andrectangular reflection by the functional plane 26a of the polarizing beam splitter 26. Said reflected S-polarized component LS enters the ~/4 phase shifting plate 27, then reflected by the reflecting plane of the reflecting plate 28, and is again transmitted by the phase shifting plate 27, thereby subjected to a rotation of the plane of polarization by 90 and thereby converted into a P-polarized component Lp*, which is transmitted by the functional plane 26a and emerges from the polarizing beam splitter 26. On the other hand, said transmitted P-polarized component Lp is rectangularly reflected by the total reflection l plane 29a of the total reflection prism 29, and emerges therefrom parallel to said converted P-polarized component Lp*.
In this polarized illuminating apparatus, as indicated by rays 1' a2, ~3, all the light entering the polarizing beam splitter 26 is received by the functional plane 26a thereof, and is split into the P-polarized component Lp and the S-polarized component Ls. Also all the S-polarized component Ls enters the phase shifting plate 27, thus`being subjected to the rotation of plane of polarization. On the other hand, said P-polarized component Lp scarcely enters the ~/4 phase shifting plate 27. Also with respect to an ' arbitrary ray, the P-polarized component Lp energing from the total reflection prism 29 and the converted P-polarized component Lp* emerging from the polarizing beam splitter 26 are mutually symmetrical in the vertical direction. Consequently, even if the light beam entering the polarizing beam splitter 26 becomes unbalanced due for example to a positional shift of the light source 1, there will result no abrupt change in the illumination intensity at the junction point of said P-polarized component Lp and said converted P-polarized component Lp*. Also since said P-polarized component Lp and said converted P-polarized component Lp* have a same optical path length, there can be prevented an imbalance in the illumination intensity - 15 - 2Q326~
l resulting from uncollimated light. This is rendered possible by a structure in which the functional plane 26a of the polarizing beam splitter 26, the ~/4 phase shifting plate 27 and the total reflection plane 29a of the total reflection prism 29 are maintained in mutual contact with predetermined angles, and is not achievable in the conventional structure employing the ~/2 phase shifting plate 13 shown in Fig. 3, because the functional plane of the polarizing beam splitter 11 is parallel to the total reflection plane of the prism 12.
Also in the present polarized illuminating apparatus, at the entry into the polarizing beam 'splitter 26, a ray obliquely entering the ~/4 phase shifting plate 27, such as ~ in Fig. 6, may be lost by transmission or reflection by said phase shifting plate 27, but such loss can be prevented by forming, on the junction plane between the polarizing beam splitter 26 and the ~/4 shifting plate 27, an optical multi-layered film which reflects a ray of a large incident angle, such as ~, and transmits the normal ray with a small incident angle.
Also an incident ray entering the total reflection plane 29a of the prism 29 with an incident angle smaller than the total reflection angle, such as ~ shown in Fig. 6, is partially lost in said P-polarized component Lp due to partial transmission, 1 but such loss can also be prevented by forming a multi-layered reflecting film or a metal reflecting film on the total reflection plane 29a.
As explained in the foregoing, the present polarized illuminating apparatus can improve the efficiency of light utilization, as the P-polarized component Lp and the S-polarized component Ls split by the polarizing beam splitter 26 can both be utilized for illuminating the light valve (not shown). Besides a remarkable improvement can be achieved in the balance of illumination intensity which has been a problem in the parallel illumination of the liquid crystal light valve (not shown) with said P-polarized component Lp and said converted P-polarized component Lp*, and there is also achieved a reduction in the distance between the polarized illuminating apparatus and the light valve, which has been difficult to achieve in the illuminating system with the synthesized light shown in Fig. 3. Thus the present invention enables compactization of the image display apparatus.
The total reflection prism Z9 may be integrally formed with a rectangular prism, positioned next to said total reflection prism 29, of the polarizing beam splitter 26.
Fig. 7 illustrates a second embodiment of the polarized illuminating apparatus of the present 20326~a l inventiOn.
The present embodiment is different from that shown in Fig. 5 in that the P-polarized component Lp, transmitted by-the functional plane 36a of a polarizing beam splitter 36 and immediately emerges therefrom, while the S-polarized component Ls reflected by said functional plane 36a is converted into a P-polarized component Lp* by a ~/4 phase shifting plate 37 and a reflecting plate 38, then rectanguIarly reflected by the total reflection plane ~--39a of a total reflection prism 39 and emerges therefrom in parallel manner to said P-polarized component Lp.
' In this polarized illuminating apparatus, the direction of the emerging light can be made same as that of the incident light, without addition of other optical components. The P-polarized component and the converted P-polarized component Lp* have mutually different optical path lengths, but can provide same advantages as those in the apparatus shown in Fig. 1.
The total reflection prism 39 may be formed integrally with a rectangular prism, positioned next to said total reflection prism 39, of the polarizing beam splitter 36.
Fig. 8 illustrates a third embodiment of the polarized illuminating apparatus of the present invention.
- 18 - 20326~Q
l In the present embodiment, the reflecting plate 28 in Fig. 5 is replaced by a rectangular prism 40, for reflecting the S-polarized component Ls, reflected by the functional plane 46a of a polarizing beam splitter 46, without formation of an unnecessary polarized component.
In the present embodiment, said S-polarized component Ls is laterally inverted with respect to the central axis thereof, then enters a ~/4 phase shifting plate 47 from the rectangular prism 40, and is converted into the P-polarized component Lp*.
Consequently said converted P-polarized component Lp*
and the P-polarized component Lp emerging from a total ' reflection prism 49 lack the symmetry explained in the apparatus shown in Fig. 1, so that the illumination intensity distribution tends to become unbalanced when the light bean entering the polarizing beam splitter 46 is unbalanced. Also the P-polarized component Lp emerging from the total reflection prism 49 and the converted P-polarized component Lp* emerging from the polarizing beam splitter 46 have mutually different optical path lengths, so that the use of uncollimated light may pose a problem. However the present embodiment provides other advantages same as those in the apparatus shown in Fig. 1.
The total reflection prism 49 may be formed integrally with a rectangular prism, positioned next ~032680 1 to said total reflection prism 49, of the polarizing beam splitter 46.
Fig. 9 illustrates a fourth embodiment of the polarized illuminating apparatus of the present invention.
The polarized illuminating apparatus of the present embodiment is composed of a polarizing beam splitter 56 having a first functional plane 56a (an evaporated film formed on one of two diagonal planes for jointing three rectangular prisms) for transmitting the P-polarized component Lp of incident light beam and perpendicularly reflecting the S-polarized component thereof, and a second functional plane 56b (an evaporated film formed on the other of said two diagonal planes) contacting at an end thereof rectangularly with said first functional plane 56a; a ~/4 phase shifting plate 57 contacting at an end thereof, with an angle of 45, with the other end of said second functional plane and adhered to a face of the polarizing beam splitter 56 opposite to the entrance face thereof; and a reflecting plate 58 having a reflecting plane adhered to said ~/4 phase shifting plate 57.
Among a parallel incident beam from a condenser lens (not shown), the S-polarized component Ls is reflected by the first functional plane 56a of the polarizing beam splitter 56 and immediately ~032G~ ~
l emerges therefrom. The P-polarized component Lp is transmitted by the first and second functional planes 56a, 56b of the polarizing beam splitter 56 and enters the ~/4 phase shifting plate 57. Said component is converted into the S-polarized component Ls* by a rotation of the plane of polarization by 90 in the phase shifting plate 57 and the reflecting plate 58, then perpendicularly reflected by the second functional plane 56b of the polarizing beam splitter 56, and emerges therefrom in a direction same as that of the above-mentioned S-polarized component Ls.
The present embodiment is not suitable for uncollimated light because said S-polarized component Is and said converted S-polarized component Ls* have mutually different optical path lengths, but provide other advantages same as those in the apparatus shown in Fig. 5. Also the apparatus of the present embodiment may be utilized as an analyzer in an image display apparatus utilizing a liquid crystal light valve (as will be explained later), because of absence of the phase shifting plate 57 and the reflecting plate 58 at the side opposite to the entrance side.
In the following there will be explained an embodiment of the image display apparatus obtained by combining the polarized illuminating apparatus of the present invention with other optical components.
Fig. 10 is a schematic view showing the - 21 - ' 2n3~&~0 1 principal part of an embodiment of the projection display apparatus utilizing the polarized illuminating apparatus shown in Fig. 9.
As shown in Fig. 10, said projection display apparatus is provided with a light source unit 100 comprising a light source 1, a reflection mirror 2, a heat ray cut-off filter 3 and a condenser lens 4; a polarized illuminating apparatus 101 shown in Fig. 9;
a cross dichroic prism 102 adhered at a face thereof 10 to the exit face of said polarized illuminating apparatus 101 and bearing reflective liquid crystal light valves 65R, 65G, 65B for red, green and blue colors respectively on other three faces; and a projection lens 10 positioned opposed to the exit face 15 of the polarized illuminating apparatus 101.
Among a white parallel light beam emerging from the light source unit 100, the S-polarized component Ls is perpendicularly reflected by a first functional plane 56a of a polarizing beam splitter 56 20 constituting the polarized illuminating apparatus 101 (cf. Fig. 9), and enters the cross dichroic prism 102.
Also the P-polarized component Lp is converted into an S-polarized component Ls* by the ~/4 phase shifting plate 57 and the reflecting plate 58 as explained 2S before, then perpendicularly reflected by the second functional plane 56b of the polarizing beam splitter 56 (cf. Fig. 9) and enters the cross dichroic prism 2Q32G~ O
1 102. Thus, said white parallel light beam is directed to the cross dichroic prism 102 after conversion into a linearly polarized beam, consisting of the S-polarized components Ls, Ls*, in the polarized illuminating apparatus 101.
Said linearly polarized beam is split by the cross dichroic prism 102 into red, green and blue light beams R, G, B, which are respectively projected toward the reflective liquid crystal light valves 65R, 65G, 65B for red, green and blue colors. The liquid crystal used in said light valves is of ECB
(electrically controlled birefringence) type or 45 TN
(twisted nematic) type, and has a property of rotating ~the plane of polarization of the incident light, depending on the voltage applied according to image signals. Consequently, the light incident to the reflective light crystal light valves 65R, 65G, 65B is linearly polarized light composed of S-polarized components, but the reflected light contains a P-polarized component according to the image signal ineach pixel. The reflected light beams are synthesized in the cross dichroic prism 102 and return to the polarized illuminating apparatus 101. In said apparatus 101, a pair of functional planes of the polarizing beam splitter 56 (Fig. 9) function as an analyzer, whereby the P-polarized component Lpo in said synthesized reflected light is transmitted and 2 ~ 3 ~
1 projected onto a screen (not shown) through the projection lens 10. A part of the S-polarized component Lso in said synthesized reflected light, entering the first functional plane 56a of the polarizing beam splitter 56 is perpendicularly reflected by said functional plane 56a and returns to the light source unit 100. Also another part of said S-polarized component Lso, entering the second functional plane 56b of the polarizing beam splitter 56 is perpendicularly reflected by said functional plane, then is converted into a P-polarized component by the ~/4 phase shifting plate 57 and the reflecting plate 58, then transmitted by the second and first functional planes 56b, 56a and returns to the light source unit 100. Consequently, in the present polarized illuminating apparatus, the polarizing beam splitter 56 functions as a complete analyzer.
The above-explained projection display apparatus provides advantages of improving the efficiency of light utilization since the white parallel light beam from the light source unit 100 can be converted, without loss, into a linearly polarized beam by the polarized illuminating apparatus 100, and significantly reducing the rear-focus length of the projection lens in comparison with that in the conventional projection display apparatus, because of separation and synthesis of beams of different colors 2~32680 l by means of the cross dichroic prism 102, thereby expanding the design freedom of the projection lens 10 and compactizing the entire display apparatus. There is also provided another advantage that the polarized illumi-nating apparatus 101 can be utilized as an analyzer.
. . .
Figs. llA and llB are respectively a side viewand a plan view of an embodiment of the projection display apparatus utilizing the polarized illuminating apparatus shown in Fig. 5.
This projection display apparatus is provided with a light source unit 100; a polarized illuminating apparatus 111 shown in Fig. 5; a mirror 77 for - perpendicularly reflecting the light beam from said polarized illuminating apparatus 111 downwards; a polarizing beam splitter 78 for perpendicularly reflecting the S-polarized component of the beam reflected by said mirror 77 toward the polarized illuminating apparatus 111 while transmitting the P-polarized component; a cross dichroic prism 102 adhered on a lateral face thereof to the exit face of said S-polarized component of the polarized beam splitter 78 and having reflective liquid crystal light valves 65R, 65G, 65B for red, green and blue colors on three other lateral faces; and a projection lens 10 positioned opposite to the side of the cross dichroic prism 112 with respect to the polarized beam splitter 78.
~0326~
l A white parallel light beam emitted from the light source unit 100 enters the polarized illuminating apparatus 111, and the P-polarized component of said white parallel beam and the converted P-polarized component obtained from the ~/4 phase shifting plate 27 and the reflecting plate 28 (both P-polarized components being hereinafter collectively called P-polarized beam) enter the mirror 77. Said P-polarized beam is totally reflected by the mirror 77 and enters the polarizing beam splitter 78.
As the plane of polarization of said P-polarized beam is S-polarized plane to the functional plane of the polarizing beam splitter 78, said beam is reflected by said plane and enters the cross dichroic prism 102.
In said prism, the P-polarized beam behaves in the same manner as in the cross dichroic prism shown in Fig. 10, and the reflected light beams, modulated by the reflective liquid crystal light valves 65R, 65G, 65B according to an image signal enter the polarizing beam splitter 78, which functions as an analyzer, as in the polarized illuminating apparatus 10 shown in Fig. 10. Thus the components, transmitted by said polarizing beam splitter 78, of the reflected light beams are projected through the projection lens 10 onto a screen (not shown) to form an image thereon.
As explained above, the projection display apparatus of the present embodiment provides, as in 2~32680 l the apparatus shown in Fig. 10, advantages of improvement in the efficiency of light utilization, expansion of design freedom of the projection lens 10, and compactization of the entire structure.
The present embodiment employs the polarized illuminating apparatus shown in Fig. 5, but the apparatus shown in Fig. 7 or 8 may naturally be employed likewise.
Also the projection display apparatus employing a transmission liquid crystal light valve as shown in Fig. 3 may be obtained by combining the polarized illuminating apparatus of the present invention shown in Fig. 5, 7, 8 or 9 with the wedge-shaped lenses 14, 15 shown in Fig. 3. Also in the projection display apparatus shown in Fig. 1 or 2, the polarized illuminating apparatus of the present invention may be positioned between the condenser lens 4 and the polarizing plate 5, or between the condenser lens 4 and the polarizing beam splitter.
The polarized illuminating apparatus explained in the foregoing has the advantage of improving the efficiency of light utilization, by emitting either of the P- and S-polarized components, separated by a polarizing beam splitter, of the incident light beam 25 and also the other component after rotation of the plane of polarization by 90 with a ~/4 phase shifting plate and a reflecting member. Consequently 20~26S0 1 the present invention enables to obtain an image display apparatus capable of brighter display.
An object of the present invention is to provide an image display apparatus equipped with an improved polarized illuminating device capable of reducing the loss in the amount of light.
The above-mentioned object can be attained, according to a first embodiment of the present invention, by an image display apparatus comprising:
a radiation source;
a generator for generating an image by modulating a polarized light beam; and directing means for directing a light beam from said radiation source toward said generator;
wherein said directing means has a conversion optical system for converting the beam from said radiation source into said polarized light beam;
said conversion optical system comprises a polarizing beam splitter for splitting the beam from said radiation source into a first beam and a second beam whose polarization planes are orthogonal to each other;
and an arrangement of a 1/4 wavelength plate and a mirror for rotating the polarization plane of said first beam to generate a third beam whose polarization plane is same as that of the second beam;
whereby said third beam is directed toward said generator through said polarizing beam splitter 203268~
..~
1 while said second beam is also directed toward said generator.
Also the above-mentioned object can be attained, according to a second embodiment of the present invention, by an image display apparatus comprising:
a radiation source;
a generator for generating an image by modulating a polarized light beam; and directing means for directing a light beam from said radiation source toward said generator;
wherein said directing means comprises a collimator for substantially collimating the beam from ~said radiation source and a conversion optical system for converting thus collimated beam into said polarized beam; and said conversion optical system comprises a polarizing beam splitter with a splitting plane inclined to the optical axis of said collimator, for splitting said collimated beam by transmitting a P-polarized beam thereof while reflecting an S-polarized beam thereof; an arrangement of a 1/4 wavelength plate and a mirror for rotating the polarization plane of said S-polarized beam to generate a polarized beam with a polarized plane coinciding with that of said P-polarized beam and directing said generated polarized beam toward a predetermined direction through said 3 203268d 1 polarizing beam splitter; and an auxiliary mirror for reflectively deflecting said P-polarized beam toward said predetermined direction.
Also the above-mentioned object can be attained, according to a third embodiment of the present invention, by an image display apparatus comprising:
a radiation source;
a generator for generating an image by 0 modulating a polarized light beam; and directing means for directing a light beam from said radiation source toward said generator;
wherein said directing means comprises a collimator for substantially collimating the beam from said radiation source and a conversion optical system for converting thus collimated beam into said polarized beam; and said conversion optical system comprises a first polarizing beam splitter with a splitting plane inclined to the optical axis of said collimator, for splitting said collimated beam by transmitting a P-polarized beam thereof while reflecting an S-polarized beam thereof in a predetermined direction; a second polarizing beam~splitter with a splitting plane inclined to the optical axis of said collimator; and an arrangement of a 1/4 wavelength plate and a mirror for receiving said P-polarized beam through said 2032~8~
1 second polarizing beam splitter, rotating the polarization plane of said P-polarized beam to generate a polarized beam with a polarization plane coinciding with that of said S-polarized beam and reflectively deflecting said generated polarized beam into said predetermined direction through said second polarizing beam splitter.
Also the above-mentioned object can be attained, according to a fourth embodiment of the present invention, by an image display apparatus comprising:
a radiation source;
a generator for generating an image by modulating a polarized light beam; and directing means for directing a light beam from said radiation source toward said generator;
wherein said directing means comprises a collimator for substantially collimating the beam from said radiation source and a conversion optical system for converting thus collimated beam into said polarized beam; and said conversion optical system comprises a polarizing beam splitter with a splitting plane inclined to the optical axis of said~collimator, for splitting said collimated beam by transmitting a P-polarized beam thereof into a predetermined direction while reflecting an S-polarized beam thereof; an 203~0 arrangement of a 1/4 wavelength plate and a mirror for rotating the polarization plane of said S-polarized beam to generate a polarized beam with a polarization plane coinciding with that of said P-polarized beam and directing said generated polarized beam toward said polarizing beam splitter; and an auxiliary mirror for receiving said polarized beam through said polarizing beam splitter and reflectively deflecting said polarized beam into said predetermined direction.
Fig. 1 is a schematic view showing the structure of an example of the conventional projection display apparatus;
Fig. 2 is a schematic view showing the structure of another example of the conventional projection display apparatus;
Fig. 3 is a schematic view showing the structure of a projection display apparatus disclosed in the Japanese Patent Application Laid-Open No. 61-90584;
Fig. 4 is a schematic view showing a drawback encountered when the parallel illumination method is employed in the projection display apparatus shown in Fig. 3;
Fig. 5 is a view of a first embodiment of the polarized illuminating apparatus of the present 6 20326~0 L invention;
Fig. 6 is a schematic view showing the optical path in the polarized illuminating apparatus shown in Fig. 5;
Fig. 7 is a view of a second embodiment of the polarized illuminating apparatus of the present invention;
Fig. 8 is a view of a third embodiment of the polarized illuminating apparatus of the present invention;
Fig. 9 is a view of a fourth embodiment of the polarized illuminating apparatus of the present invention;
. Fig. 10 is a partial view of an embodiment of lS a projection display apparatus provided with the polarized illuminating apparatus shown in Fig. 9; and ~ Figs. llA and llB are respectively a lateral view and a plan view of an embodiment of a projection display apparatus provided with the polarized illuminating apparatus shown in Fig. 5.
Fig. 1 is a schematic view showing the principal structure of an example of the conventional image display apparatus.
Said display apparatus is provided with a light source 1 composed for example of a halogen lamp or a metal halide lamp; a mirror 2 reflecting a part of the light emitted by said light source l; a heat ray cut-off filter 3 for absorbing or reflecting the heat ray in the light entering directly from the light source 1 or indirect~y from the mirror 2; a condenser lens 4 for converting the light, after removal of the heat ray, into a parallel beam; a polarizer 5 for converting said parallel light beam into linearly polarized light; a liquid crystal light valve 7 for modulating said linearly polarized light according to an image signal; a polarizer 8 for transmitting only a component, parallel to the transmission axis thereof, Of said modulated linearly polarized light; and a projection lens lO for projecting the linearly polarized light, transmitted by said polarizer 8, in 20~2gg~
l a magnified scale onto an unrepresented screen.
Fig. 2 is a schematic view showing the principal part of another example of such conventional projection display apparatus.
Said apparatus is equipped with two polarizing beam splitters 6, 9 respectively in front of and behind the light crystal light valve 7, in place for the two polarizers 5, 8 in the apparatus shown in Fig.
1.
The projection display apparatus shown in Figs. 1 and 2 are associated with a drawback that the efficiency of ulitization of light does not exceed 50 %, since, within the light emitted by the light ~source 1, a linearly polarized component transmitted by the polarizing beam splitter 6 alone is utilized for illuminating the light crystal light valve 7 while the perpendicularly polarized component is lost.
Fig. 3 shows a projection display apparatus disclosed in the Japanese Patent Application Laid-Open No. 61-90584 for rectifying said drawback.
In said projection display apparatus the parallel light beam emerging from the condenser lens 4 enters a polarizing beam splitter 11, and the P-polarized component Lp is transmitted by the functional plane (an evaporated film formed on a diagonal plane between two rectangular prisms) lla of said polarizing beam splitter 11, while the -1 S-polarized component Ls is perpendicularly reflected to enter a total reflection prism 12. Being perpendicularly reflected again in said prism 12, the S-polarized component Ls emerges from said prism 12 in a direction same as that of the P-polarized component Lp. The S-polarized component Ls is polarized in a direction parallel to the functional plane lla of the polarizing beam splitter 11, and the P-polarized component Lp is polarized in a direction perpendicular to that of the S-polarized component.
At the exit side of the total reflection 12 there is provided a ~/2-phase shifting plate 13, whereby said S-polarized component L2 is subjected to ~ rotation of the polarizing direction by 90- and is converted into a P-polarized component Lp*. Also at the exit side of the polarizing beam splitter 11 and the A/2-phase shifting plate 13 there are respectively provided wedge-shaped lenses 14, 15 for light path deflection, whereby the P-polarized component Lp transmitted by said polarizing beam splitter 11 and the P-polarized component Lp*
converted by the ~/2-phase shifting plate 13 are subjected to light path deflection and mutually cross at a point P0 on the entrance face of the liquid crystal light valve 7, thereby providing a synthesized light.
Consequently such projection display apparatus 1 can illuminate the liquid crystal light valve 7 with both the S-polarized component Ls and the P-polarized component Lp separated by the polarizing beam splitter 11 and can therefore double the efficiency of light utilization in comparison with the apparatus shown in Fig. 2.
However, in the projection display apparatus disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 61-90584, since the P-polarized component Lp and the P-polarized component Lp* converted by the ~/2-phase shifting plate 13 respectively enter the liquid crystal light valve with an angle 6 as shown in Fig. 3, it is necessary to ~select a considerably large distance from the wedge-shaped lenses 14, 15 to the liquid crystal light valve7 in order to reduce said incident angle e if the light valve 7 shows significant deterioration of characteristics depending on the incident angle.
For avoiding such drawback, there is conceived a parallel illuminating method in which the wedge-shaped lenses 14, 15 shown in Fig. 3 are removed, whereby said P-polarized component Lp and said converted P-polarized component Lp* enter the liquid crystal light valve 7 in mutually parallel state.
However, such parallel illumination method, if applied to the projection display apparatus disclosed in the Japanese Patent Application Laid-Open No. 61-90584, 1 cannot provide the expected result because the P-polarized component Lp and the converted P-polarized component Lp* are not complete unless the light source 1 is a complete point or linear source providing completely parallel beams from the condenser lens 4.
This will be explained further with reference to Fig.
4.
In case the light from a light source 1 with a finite diameter ~ is condensed by a condenser lens 4 at a distance ~, the light emerging therefrom is not completely parallel but is spread within an angular range 2 ~( ~ctan 1 (~ /2)/ ~). A ray a contained in thus obtain non-parallel beam enters the A/2-phase ~shifting plate 13 without the function of the lS polarizing beam splitter 11 and emerges from said phase shifting plate 13 with the P- and S-polarized components. Also a ray ~ is converted by the polarizing beam splitter 11 into the S-polarized component Ls, which is then reflected by the total reflection prism 12 and reflected again by the polarizing beam splitter 11. It thus emerges as a P-polarized component Lp* from another position of the /2-phase shifting plate 13 as indicated by a ray ~1' or is lost by absorpt,on or transmission at the surface of the phase shifting plate 13 as indicated by a ray ~2-203~6~
Now the present invention will be clarified in greater detail by embodiments thereof shown in the attached drawings.
Fig. 5 is a schematic view of a first embodiment of the polarized illuminating apparatus of the present invention, and Fig. 6 is a view showing the optical path thereof.
Said polarized illuminating apparatus is composed of a polarizing beam splitter 26 having a function plane (an evaporated film formed on a diagonal plane at which two rectangular prisms are mutually adhered) for transmitting the P-polarized component Lp of a parallel light beam emerging from a condenser lens 4 while rectangularly reflecting the S-polarized component Ls; a total reflection prism 29 provided with a total reflection plane 29a contacting at an end thereof rectangularly with an end of the functional plane 26a of said polarizing beam 20326~
1 splitter 26 and serving to rectangularly reflect said transmitted P-polarized component Lp; a ~/4 phase shifting plate 27 contacting at an end thereof, at an angle of 45, with an end of the functional plane 26a of said polarizing beam splitter and with an end of the total reflection plane 29a of said total reflection prism 29, and adapted to receive said reflected S-polarized component Ls; and a reflecting plate 28 having a reflecting plane, composed of an aluminum evaporated film or an optical multi-layered film, adhered to said ~/4 phase shifting plate 27.
In said polarized illuminating apparatus, the parallel light beam emerging from the condenser lens 4 'is split into the P-polarized component Lp and the S-polarized component Ls, by respective transmission andrectangular reflection by the functional plane 26a of the polarizing beam splitter 26. Said reflected S-polarized component LS enters the ~/4 phase shifting plate 27, then reflected by the reflecting plane of the reflecting plate 28, and is again transmitted by the phase shifting plate 27, thereby subjected to a rotation of the plane of polarization by 90 and thereby converted into a P-polarized component Lp*, which is transmitted by the functional plane 26a and emerges from the polarizing beam splitter 26. On the other hand, said transmitted P-polarized component Lp is rectangularly reflected by the total reflection l plane 29a of the total reflection prism 29, and emerges therefrom parallel to said converted P-polarized component Lp*.
In this polarized illuminating apparatus, as indicated by rays 1' a2, ~3, all the light entering the polarizing beam splitter 26 is received by the functional plane 26a thereof, and is split into the P-polarized component Lp and the S-polarized component Ls. Also all the S-polarized component Ls enters the phase shifting plate 27, thus`being subjected to the rotation of plane of polarization. On the other hand, said P-polarized component Lp scarcely enters the ~/4 phase shifting plate 27. Also with respect to an ' arbitrary ray, the P-polarized component Lp energing from the total reflection prism 29 and the converted P-polarized component Lp* emerging from the polarizing beam splitter 26 are mutually symmetrical in the vertical direction. Consequently, even if the light beam entering the polarizing beam splitter 26 becomes unbalanced due for example to a positional shift of the light source 1, there will result no abrupt change in the illumination intensity at the junction point of said P-polarized component Lp and said converted P-polarized component Lp*. Also since said P-polarized component Lp and said converted P-polarized component Lp* have a same optical path length, there can be prevented an imbalance in the illumination intensity - 15 - 2Q326~
l resulting from uncollimated light. This is rendered possible by a structure in which the functional plane 26a of the polarizing beam splitter 26, the ~/4 phase shifting plate 27 and the total reflection plane 29a of the total reflection prism 29 are maintained in mutual contact with predetermined angles, and is not achievable in the conventional structure employing the ~/2 phase shifting plate 13 shown in Fig. 3, because the functional plane of the polarizing beam splitter 11 is parallel to the total reflection plane of the prism 12.
Also in the present polarized illuminating apparatus, at the entry into the polarizing beam 'splitter 26, a ray obliquely entering the ~/4 phase shifting plate 27, such as ~ in Fig. 6, may be lost by transmission or reflection by said phase shifting plate 27, but such loss can be prevented by forming, on the junction plane between the polarizing beam splitter 26 and the ~/4 shifting plate 27, an optical multi-layered film which reflects a ray of a large incident angle, such as ~, and transmits the normal ray with a small incident angle.
Also an incident ray entering the total reflection plane 29a of the prism 29 with an incident angle smaller than the total reflection angle, such as ~ shown in Fig. 6, is partially lost in said P-polarized component Lp due to partial transmission, 1 but such loss can also be prevented by forming a multi-layered reflecting film or a metal reflecting film on the total reflection plane 29a.
As explained in the foregoing, the present polarized illuminating apparatus can improve the efficiency of light utilization, as the P-polarized component Lp and the S-polarized component Ls split by the polarizing beam splitter 26 can both be utilized for illuminating the light valve (not shown). Besides a remarkable improvement can be achieved in the balance of illumination intensity which has been a problem in the parallel illumination of the liquid crystal light valve (not shown) with said P-polarized component Lp and said converted P-polarized component Lp*, and there is also achieved a reduction in the distance between the polarized illuminating apparatus and the light valve, which has been difficult to achieve in the illuminating system with the synthesized light shown in Fig. 3. Thus the present invention enables compactization of the image display apparatus.
The total reflection prism Z9 may be integrally formed with a rectangular prism, positioned next to said total reflection prism 29, of the polarizing beam splitter 26.
Fig. 7 illustrates a second embodiment of the polarized illuminating apparatus of the present 20326~a l inventiOn.
The present embodiment is different from that shown in Fig. 5 in that the P-polarized component Lp, transmitted by-the functional plane 36a of a polarizing beam splitter 36 and immediately emerges therefrom, while the S-polarized component Ls reflected by said functional plane 36a is converted into a P-polarized component Lp* by a ~/4 phase shifting plate 37 and a reflecting plate 38, then rectanguIarly reflected by the total reflection plane ~--39a of a total reflection prism 39 and emerges therefrom in parallel manner to said P-polarized component Lp.
' In this polarized illuminating apparatus, the direction of the emerging light can be made same as that of the incident light, without addition of other optical components. The P-polarized component and the converted P-polarized component Lp* have mutually different optical path lengths, but can provide same advantages as those in the apparatus shown in Fig. 1.
The total reflection prism 39 may be formed integrally with a rectangular prism, positioned next to said total reflection prism 39, of the polarizing beam splitter 36.
Fig. 8 illustrates a third embodiment of the polarized illuminating apparatus of the present invention.
- 18 - 20326~Q
l In the present embodiment, the reflecting plate 28 in Fig. 5 is replaced by a rectangular prism 40, for reflecting the S-polarized component Ls, reflected by the functional plane 46a of a polarizing beam splitter 46, without formation of an unnecessary polarized component.
In the present embodiment, said S-polarized component Ls is laterally inverted with respect to the central axis thereof, then enters a ~/4 phase shifting plate 47 from the rectangular prism 40, and is converted into the P-polarized component Lp*.
Consequently said converted P-polarized component Lp*
and the P-polarized component Lp emerging from a total ' reflection prism 49 lack the symmetry explained in the apparatus shown in Fig. 1, so that the illumination intensity distribution tends to become unbalanced when the light bean entering the polarizing beam splitter 46 is unbalanced. Also the P-polarized component Lp emerging from the total reflection prism 49 and the converted P-polarized component Lp* emerging from the polarizing beam splitter 46 have mutually different optical path lengths, so that the use of uncollimated light may pose a problem. However the present embodiment provides other advantages same as those in the apparatus shown in Fig. 1.
The total reflection prism 49 may be formed integrally with a rectangular prism, positioned next ~032680 1 to said total reflection prism 49, of the polarizing beam splitter 46.
Fig. 9 illustrates a fourth embodiment of the polarized illuminating apparatus of the present invention.
The polarized illuminating apparatus of the present embodiment is composed of a polarizing beam splitter 56 having a first functional plane 56a (an evaporated film formed on one of two diagonal planes for jointing three rectangular prisms) for transmitting the P-polarized component Lp of incident light beam and perpendicularly reflecting the S-polarized component thereof, and a second functional plane 56b (an evaporated film formed on the other of said two diagonal planes) contacting at an end thereof rectangularly with said first functional plane 56a; a ~/4 phase shifting plate 57 contacting at an end thereof, with an angle of 45, with the other end of said second functional plane and adhered to a face of the polarizing beam splitter 56 opposite to the entrance face thereof; and a reflecting plate 58 having a reflecting plane adhered to said ~/4 phase shifting plate 57.
Among a parallel incident beam from a condenser lens (not shown), the S-polarized component Ls is reflected by the first functional plane 56a of the polarizing beam splitter 56 and immediately ~032G~ ~
l emerges therefrom. The P-polarized component Lp is transmitted by the first and second functional planes 56a, 56b of the polarizing beam splitter 56 and enters the ~/4 phase shifting plate 57. Said component is converted into the S-polarized component Ls* by a rotation of the plane of polarization by 90 in the phase shifting plate 57 and the reflecting plate 58, then perpendicularly reflected by the second functional plane 56b of the polarizing beam splitter 56, and emerges therefrom in a direction same as that of the above-mentioned S-polarized component Ls.
The present embodiment is not suitable for uncollimated light because said S-polarized component Is and said converted S-polarized component Ls* have mutually different optical path lengths, but provide other advantages same as those in the apparatus shown in Fig. 5. Also the apparatus of the present embodiment may be utilized as an analyzer in an image display apparatus utilizing a liquid crystal light valve (as will be explained later), because of absence of the phase shifting plate 57 and the reflecting plate 58 at the side opposite to the entrance side.
In the following there will be explained an embodiment of the image display apparatus obtained by combining the polarized illuminating apparatus of the present invention with other optical components.
Fig. 10 is a schematic view showing the - 21 - ' 2n3~&~0 1 principal part of an embodiment of the projection display apparatus utilizing the polarized illuminating apparatus shown in Fig. 9.
As shown in Fig. 10, said projection display apparatus is provided with a light source unit 100 comprising a light source 1, a reflection mirror 2, a heat ray cut-off filter 3 and a condenser lens 4; a polarized illuminating apparatus 101 shown in Fig. 9;
a cross dichroic prism 102 adhered at a face thereof 10 to the exit face of said polarized illuminating apparatus 101 and bearing reflective liquid crystal light valves 65R, 65G, 65B for red, green and blue colors respectively on other three faces; and a projection lens 10 positioned opposed to the exit face 15 of the polarized illuminating apparatus 101.
Among a white parallel light beam emerging from the light source unit 100, the S-polarized component Ls is perpendicularly reflected by a first functional plane 56a of a polarizing beam splitter 56 20 constituting the polarized illuminating apparatus 101 (cf. Fig. 9), and enters the cross dichroic prism 102.
Also the P-polarized component Lp is converted into an S-polarized component Ls* by the ~/4 phase shifting plate 57 and the reflecting plate 58 as explained 2S before, then perpendicularly reflected by the second functional plane 56b of the polarizing beam splitter 56 (cf. Fig. 9) and enters the cross dichroic prism 2Q32G~ O
1 102. Thus, said white parallel light beam is directed to the cross dichroic prism 102 after conversion into a linearly polarized beam, consisting of the S-polarized components Ls, Ls*, in the polarized illuminating apparatus 101.
Said linearly polarized beam is split by the cross dichroic prism 102 into red, green and blue light beams R, G, B, which are respectively projected toward the reflective liquid crystal light valves 65R, 65G, 65B for red, green and blue colors. The liquid crystal used in said light valves is of ECB
(electrically controlled birefringence) type or 45 TN
(twisted nematic) type, and has a property of rotating ~the plane of polarization of the incident light, depending on the voltage applied according to image signals. Consequently, the light incident to the reflective light crystal light valves 65R, 65G, 65B is linearly polarized light composed of S-polarized components, but the reflected light contains a P-polarized component according to the image signal ineach pixel. The reflected light beams are synthesized in the cross dichroic prism 102 and return to the polarized illuminating apparatus 101. In said apparatus 101, a pair of functional planes of the polarizing beam splitter 56 (Fig. 9) function as an analyzer, whereby the P-polarized component Lpo in said synthesized reflected light is transmitted and 2 ~ 3 ~
1 projected onto a screen (not shown) through the projection lens 10. A part of the S-polarized component Lso in said synthesized reflected light, entering the first functional plane 56a of the polarizing beam splitter 56 is perpendicularly reflected by said functional plane 56a and returns to the light source unit 100. Also another part of said S-polarized component Lso, entering the second functional plane 56b of the polarizing beam splitter 56 is perpendicularly reflected by said functional plane, then is converted into a P-polarized component by the ~/4 phase shifting plate 57 and the reflecting plate 58, then transmitted by the second and first functional planes 56b, 56a and returns to the light source unit 100. Consequently, in the present polarized illuminating apparatus, the polarizing beam splitter 56 functions as a complete analyzer.
The above-explained projection display apparatus provides advantages of improving the efficiency of light utilization since the white parallel light beam from the light source unit 100 can be converted, without loss, into a linearly polarized beam by the polarized illuminating apparatus 100, and significantly reducing the rear-focus length of the projection lens in comparison with that in the conventional projection display apparatus, because of separation and synthesis of beams of different colors 2~32680 l by means of the cross dichroic prism 102, thereby expanding the design freedom of the projection lens 10 and compactizing the entire display apparatus. There is also provided another advantage that the polarized illumi-nating apparatus 101 can be utilized as an analyzer.
. . .
Figs. llA and llB are respectively a side viewand a plan view of an embodiment of the projection display apparatus utilizing the polarized illuminating apparatus shown in Fig. 5.
This projection display apparatus is provided with a light source unit 100; a polarized illuminating apparatus 111 shown in Fig. 5; a mirror 77 for - perpendicularly reflecting the light beam from said polarized illuminating apparatus 111 downwards; a polarizing beam splitter 78 for perpendicularly reflecting the S-polarized component of the beam reflected by said mirror 77 toward the polarized illuminating apparatus 111 while transmitting the P-polarized component; a cross dichroic prism 102 adhered on a lateral face thereof to the exit face of said S-polarized component of the polarized beam splitter 78 and having reflective liquid crystal light valves 65R, 65G, 65B for red, green and blue colors on three other lateral faces; and a projection lens 10 positioned opposite to the side of the cross dichroic prism 112 with respect to the polarized beam splitter 78.
~0326~
l A white parallel light beam emitted from the light source unit 100 enters the polarized illuminating apparatus 111, and the P-polarized component of said white parallel beam and the converted P-polarized component obtained from the ~/4 phase shifting plate 27 and the reflecting plate 28 (both P-polarized components being hereinafter collectively called P-polarized beam) enter the mirror 77. Said P-polarized beam is totally reflected by the mirror 77 and enters the polarizing beam splitter 78.
As the plane of polarization of said P-polarized beam is S-polarized plane to the functional plane of the polarizing beam splitter 78, said beam is reflected by said plane and enters the cross dichroic prism 102.
In said prism, the P-polarized beam behaves in the same manner as in the cross dichroic prism shown in Fig. 10, and the reflected light beams, modulated by the reflective liquid crystal light valves 65R, 65G, 65B according to an image signal enter the polarizing beam splitter 78, which functions as an analyzer, as in the polarized illuminating apparatus 10 shown in Fig. 10. Thus the components, transmitted by said polarizing beam splitter 78, of the reflected light beams are projected through the projection lens 10 onto a screen (not shown) to form an image thereon.
As explained above, the projection display apparatus of the present embodiment provides, as in 2~32680 l the apparatus shown in Fig. 10, advantages of improvement in the efficiency of light utilization, expansion of design freedom of the projection lens 10, and compactization of the entire structure.
The present embodiment employs the polarized illuminating apparatus shown in Fig. 5, but the apparatus shown in Fig. 7 or 8 may naturally be employed likewise.
Also the projection display apparatus employing a transmission liquid crystal light valve as shown in Fig. 3 may be obtained by combining the polarized illuminating apparatus of the present invention shown in Fig. 5, 7, 8 or 9 with the wedge-shaped lenses 14, 15 shown in Fig. 3. Also in the projection display apparatus shown in Fig. 1 or 2, the polarized illuminating apparatus of the present invention may be positioned between the condenser lens 4 and the polarizing plate 5, or between the condenser lens 4 and the polarizing beam splitter.
The polarized illuminating apparatus explained in the foregoing has the advantage of improving the efficiency of light utilization, by emitting either of the P- and S-polarized components, separated by a polarizing beam splitter, of the incident light beam 25 and also the other component after rotation of the plane of polarization by 90 with a ~/4 phase shifting plate and a reflecting member. Consequently 20~26S0 1 the present invention enables to obtain an image display apparatus capable of brighter display.
Claims (19)
1. An image display apparatus comprising:
a radiation source;
a generator for generating an image by modulating a polarized beam; and directing means for directing a beam from said radiation source to said generator;
wherein said directing means comprises a conversion optical system for converting the beam from said radiation source into said polarized beam; and said conversion optical system includes a polarizing beam splitter for splitting the beam from said radiation source into a first beam and a secondbeam of mutually orthogonal planes of polarization; and an arrangement of a 1/4 wavelength plate and a mirror for rotating the plane of polarization of said first beam to generate a third beam of a plane of polarization the same as that of said second beam; and for directing said third beam to said polarizing beam splitter wherein said conversion optical system generates said third beam without redirecting said first beam to said radiation source and directs said second and third beams to said generator.
a radiation source;
a generator for generating an image by modulating a polarized beam; and directing means for directing a beam from said radiation source to said generator;
wherein said directing means comprises a conversion optical system for converting the beam from said radiation source into said polarized beam; and said conversion optical system includes a polarizing beam splitter for splitting the beam from said radiation source into a first beam and a secondbeam of mutually orthogonal planes of polarization; and an arrangement of a 1/4 wavelength plate and a mirror for rotating the plane of polarization of said first beam to generate a third beam of a plane of polarization the same as that of said second beam; and for directing said third beam to said polarizing beam splitter wherein said conversion optical system generates said third beam without redirecting said first beam to said radiation source and directs said second and third beams to said generator.
2. An apparatus according to claim 1, wherein said directing means has a collimator for converting the beam from said radiation source into a substantially parallel beam, which is introduced into said conversion optical system.
3. An apparatus according to claim 1 or 2, wherein said polarizing beam splitter is adapted to generate said first beam by reflecting the S-polarized component of the beam from said radiation source and to generate said second beam by transmitting the P-polarized component of said beam.
4. An apparatus according to claim 3, wherein said conversion optical system is so constructed as to direct said second beam in a predetermined direction and has an auxiliary mirror for reflecting said third beam to said predetermined direction.
5. An apparatus according to claim 3, wherein said conversion optical system is so constructed as to direct said third beam to a predetermined direction and has an auxiliary mirror for reflecting said second beam to said predetermined direction.
6. An apparatus according to claim 1, 2, 4 or 5, further comprising a projection optical system for projecting said image onto a predetermined plane.
7. An apparatus according to claim 3, further comprising a projection optical system for projecting said image onto a predetermined plane.
8. An image display apparatus comprising:
a radiation source;
a generator for generating an image by modulating a polarized beam; and directing means for directing a beam from said radiation source to said generator;
wherein said directing means comprises a collimator for substantially collimating the beam from said radiation source and a conversion optical system for converting the collimated beam into said polarized beam, and wherein said conversion optical system includes a polarizing beam splitter provided with a splitting surface, inclined to the optical axis of saidcollimator, for splitting said collimated beam by transmitting the P-polarized beam thereof and reflecting the S-polarized beam thereof; and arrangement of a 1/4 wavelength plate and a mirror for rotating the plane of polarization of saidS-polarized beam to cause the polarization plane thereof to be coincident with the plane of polarization of said P-polarized beam and directing said S-polarized beam to a predetermined direction through said polarizing beam splitter without redirecting said S-polarized beam to said radiation source; and an auxiliary mirror for reflectively deflecting said P-polarized beam to said predetermined direction.
a radiation source;
a generator for generating an image by modulating a polarized beam; and directing means for directing a beam from said radiation source to said generator;
wherein said directing means comprises a collimator for substantially collimating the beam from said radiation source and a conversion optical system for converting the collimated beam into said polarized beam, and wherein said conversion optical system includes a polarizing beam splitter provided with a splitting surface, inclined to the optical axis of saidcollimator, for splitting said collimated beam by transmitting the P-polarized beam thereof and reflecting the S-polarized beam thereof; and arrangement of a 1/4 wavelength plate and a mirror for rotating the plane of polarization of saidS-polarized beam to cause the polarization plane thereof to be coincident with the plane of polarization of said P-polarized beam and directing said S-polarized beam to a predetermined direction through said polarizing beam splitter without redirecting said S-polarized beam to said radiation source; and an auxiliary mirror for reflectively deflecting said P-polarized beam to said predetermined direction.
9. An apparatus according to claim 8, further comprising a projection optical system for projecting said image onto a predetermined plane.
10. An image display apparatus comprising:
a radiation source;
a generator for generating an image by modulating a polarized beam; and directing means for directing a beam from said radiation source to said generator;
wherein said directing means comprises a collimator for substantially collimating the beam from said radiation source and a conversion optical system for converting the thus collimated beam into said polarized beam,and wherein said conversion optical system includes a polarizing beam splitter provided with a splitting surface, inclined to the optical axis of saidcollimator, for splitting said collimated beam by transmitting the P-polarized beam thereof and reflecting the S-polarized beam thereof into a predetermined direction; a second polarizing beam splitter provided with a splitting surface inclined to the optical axis of said collimator; and an arrangement of a 1/4 wavelength plate and a mirror for receiving said P-polarized beam through said second beam splitter, rotating the plane of polarization of said P-polarized beam to cause the polarization plane thereof to be coincident with the plane of polarization of said P-polarized beam, and causing said second polarizing beam splitter to reflect said P-polarized beam into said predetermined direction without redirecting said P-polarized beam to said radiation source.
a radiation source;
a generator for generating an image by modulating a polarized beam; and directing means for directing a beam from said radiation source to said generator;
wherein said directing means comprises a collimator for substantially collimating the beam from said radiation source and a conversion optical system for converting the thus collimated beam into said polarized beam,and wherein said conversion optical system includes a polarizing beam splitter provided with a splitting surface, inclined to the optical axis of saidcollimator, for splitting said collimated beam by transmitting the P-polarized beam thereof and reflecting the S-polarized beam thereof into a predetermined direction; a second polarizing beam splitter provided with a splitting surface inclined to the optical axis of said collimator; and an arrangement of a 1/4 wavelength plate and a mirror for receiving said P-polarized beam through said second beam splitter, rotating the plane of polarization of said P-polarized beam to cause the polarization plane thereof to be coincident with the plane of polarization of said P-polarized beam, and causing said second polarizing beam splitter to reflect said P-polarized beam into said predetermined direction without redirecting said P-polarized beam to said radiation source.
11. An apparatus according to claim 10 further comprising a projection optical system for projecting said image onto a predetermined plane.
12. An image display apparatus comprising:
a radiation source;
a generator for generating an image by modulating a polarized beam; and directing means for directing the beam from said radiation source to said generator;
wherein said directing means has a collimator for substantially collimating the beam from said radiation source and a conversion optical system for converting the thus collimated beam into said polarized beam; and wherein said conversion optical system includes a polarizing beam splitter provided with a splitting surface, inclined to the optical axis of saidcollimator, for splitting said collimated beam by transmitting the P-polarized beam thereof to a predetermined direction and reflecting the S-polarized beam thereof; an arrangement of a 1/4 wavelength plate and a mirror for rotating the plane of polarization of said S-polarized beam to cause the polarization of saidS-polarized beam to be coincident with the plane of polarization of said P-polarized beam and directing said S-polarized beam to said polarizing beam splitter without directing said S-polarized beam to said radiation source; and an auxiliary mirror receiving said S-polarized beam through said polarized beam splitter and reflecting it to said predetermined direction.
a radiation source;
a generator for generating an image by modulating a polarized beam; and directing means for directing the beam from said radiation source to said generator;
wherein said directing means has a collimator for substantially collimating the beam from said radiation source and a conversion optical system for converting the thus collimated beam into said polarized beam; and wherein said conversion optical system includes a polarizing beam splitter provided with a splitting surface, inclined to the optical axis of saidcollimator, for splitting said collimated beam by transmitting the P-polarized beam thereof to a predetermined direction and reflecting the S-polarized beam thereof; an arrangement of a 1/4 wavelength plate and a mirror for rotating the plane of polarization of said S-polarized beam to cause the polarization of saidS-polarized beam to be coincident with the plane of polarization of said P-polarized beam and directing said S-polarized beam to said polarizing beam splitter without directing said S-polarized beam to said radiation source; and an auxiliary mirror receiving said S-polarized beam through said polarized beam splitter and reflecting it to said predetermined direction.
13. An apparatus according to claim 12, further comprising a projection optical system for projecting said image onto a predetermined plane.
14. A projector comprising:
a radiation source;
a modulator for reflecting a polarized beam incident thereon and for generating a reflection beam indicative of an image by modulating the polarization plane of said polarized beam incident thereon according to a video signal;
a converter including a polarizing beam splitter for splitting a beam from said radiation source into P- and S-polarized components, said converter generating said polarized beam by making the polarization planes of said polarized components parallel with each other wherein said polarizing beam splitter is arranged in a path for said reflection beam so as to function as an analyzer; and a projection optical system for receiving said reflection beam through said polarizing beam splitter and for projecting said image with said beam.
a radiation source;
a modulator for reflecting a polarized beam incident thereon and for generating a reflection beam indicative of an image by modulating the polarization plane of said polarized beam incident thereon according to a video signal;
a converter including a polarizing beam splitter for splitting a beam from said radiation source into P- and S-polarized components, said converter generating said polarized beam by making the polarization planes of said polarized components parallel with each other wherein said polarizing beam splitter is arranged in a path for said reflection beam so as to function as an analyzer; and a projection optical system for receiving said reflection beam through said polarizing beam splitter and for projecting said image with said beam.
15. A projector according to claim 14 wherein said modulator has a liquid crystal panel.
16. A light modulating system, comprising:
a radiation source;
a modulator for reflecting a polarized beam incident thereon and modulating a polarization plane of said polarized beam to generate a reflected beam; and a converter including a polarizing beam splitter for splitting a beam from said radiation source into P- and S-polarized components, said converter generating said polarized beam by making the polarization planes of said polarized components parallel with each other and synthesizing them, wherein said polarizing beam splitter is arranged in a path for said reflection beam so as to function as an analyzer.
a radiation source;
a modulator for reflecting a polarized beam incident thereon and modulating a polarization plane of said polarized beam to generate a reflected beam; and a converter including a polarizing beam splitter for splitting a beam from said radiation source into P- and S-polarized components, said converter generating said polarized beam by making the polarization planes of said polarized components parallel with each other and synthesizing them, wherein said polarizing beam splitter is arranged in a path for said reflection beam so as to function as an analyzer.
17. An image display apparatus comprising:
a radiation source;
a liquid crystal panel for generating an image by modulating a polarized beam having a predetermined plane of polarization;
directing means for directing a beam from said radiation source to said generator;
wherein said directing means comprises a conversion optical system for converting the beam from said radiation source into said polarized beam; and said conversion optical system includes a polarizing beam splitter for splitting the beam from said radiation source into a first beam and a secondbeam of mutually orthogonal planes of polarization; and an arrangement of a 1/4 wavelength plate and a mirror for rotating the plane of polarization of said first beam to generate a third beam of a plane of polarization same as that of said second beam; and is adapted to direct said third beam to said generator through said polarizing beam splitter and also to direct said second beam to said generator wherein said second beam and said third beam have said predetermined plane of polarization and wherein said conversion optical system generates said third beam without redirecting said first beam to said radiation source and directs said second and third beams to said generator.
a radiation source;
a liquid crystal panel for generating an image by modulating a polarized beam having a predetermined plane of polarization;
directing means for directing a beam from said radiation source to said generator;
wherein said directing means comprises a conversion optical system for converting the beam from said radiation source into said polarized beam; and said conversion optical system includes a polarizing beam splitter for splitting the beam from said radiation source into a first beam and a secondbeam of mutually orthogonal planes of polarization; and an arrangement of a 1/4 wavelength plate and a mirror for rotating the plane of polarization of said first beam to generate a third beam of a plane of polarization same as that of said second beam; and is adapted to direct said third beam to said generator through said polarizing beam splitter and also to direct said second beam to said generator wherein said second beam and said third beam have said predetermined plane of polarization and wherein said conversion optical system generates said third beam without redirecting said first beam to said radiation source and directs said second and third beams to said generator.
18. An image display apparatus comprising:
a radiation source;
a liquid crystal panel for generating an image by modulating a polarized beam having a plane of polarization same as a direction of liquid crystal molecules oriented at incident side of said liquid crystal panel;
direction means for directing a beam from said radiation source to said generator;
wherein said directing means comprises a conversion optical system for converting the beam from said radiation source into said polarized beam; and said conversion optical system includes a polarizing beam splitter for splitting the beam from said radiation source into a first beam and a secondbeam of mutually orthogonal planes of polarization; and an arrangement of a 1/4 wavelength plate and a mirror for rotating the plane of polarization of said first beam to generate a third beam of a plane of polarization same as that of said second beam; and is adapted to direct said third beam to said generator through said polarizing beam splitter and also to direct said second beam to said generator wherein said second beam and said third beam have said predetermined plane of polarization wherein said conversion optical system generates said third beam without redirecting said first beam to said radiation source and directs said second and third beams to said generator.
a radiation source;
a liquid crystal panel for generating an image by modulating a polarized beam having a plane of polarization same as a direction of liquid crystal molecules oriented at incident side of said liquid crystal panel;
direction means for directing a beam from said radiation source to said generator;
wherein said directing means comprises a conversion optical system for converting the beam from said radiation source into said polarized beam; and said conversion optical system includes a polarizing beam splitter for splitting the beam from said radiation source into a first beam and a secondbeam of mutually orthogonal planes of polarization; and an arrangement of a 1/4 wavelength plate and a mirror for rotating the plane of polarization of said first beam to generate a third beam of a plane of polarization same as that of said second beam; and is adapted to direct said third beam to said generator through said polarizing beam splitter and also to direct said second beam to said generator wherein said second beam and said third beam have said predetermined plane of polarization wherein said conversion optical system generates said third beam without redirecting said first beam to said radiation source and directs said second and third beams to said generator.
19. An image forming apparatus comprising:
a radiation source;
a generator for generating an image by modulating a polarized beam; and directing means for directing a beam from said radiation source to said generator;
wherein said directing means comprises a conversion optical system for converting the beam from said radiation source into said polarized beam; and said conversion optical system includes a polarizing beam splitter for splitting the beam from said radiation source into a first beam and a secondbeam of mutually orthogonal planes of polarization; and an arrangement of a 1/4 wavelength plate and a mirror for rotating the plane of polarization of said first beam to generate a third beam of a plane of polarization the same as that of said second beam; and for directing said third beam to said polarizing beam splitter wherein said conversion optical system generates said third beam without redirecting said first beam to said radiation source and directs said second and third beams to said generator.
a radiation source;
a generator for generating an image by modulating a polarized beam; and directing means for directing a beam from said radiation source to said generator;
wherein said directing means comprises a conversion optical system for converting the beam from said radiation source into said polarized beam; and said conversion optical system includes a polarizing beam splitter for splitting the beam from said radiation source into a first beam and a secondbeam of mutually orthogonal planes of polarization; and an arrangement of a 1/4 wavelength plate and a mirror for rotating the plane of polarization of said first beam to generate a third beam of a plane of polarization the same as that of said second beam; and for directing said third beam to said polarizing beam splitter wherein said conversion optical system generates said third beam without redirecting said first beam to said radiation source and directs said second and third beams to said generator.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1330033A JP2752751B2 (en) | 1989-12-20 | 1989-12-20 | Display device |
| JP1-330033 | 1989-12-20 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2032680C true CA2032680C (en) | 1994-12-20 |
Family
ID=18228024
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2032680 Expired - Lifetime CA2032680C (en) | 1989-12-20 | 1990-12-19 | Image display apparatus |
Country Status (2)
| Country | Link |
|---|---|
| JP (1) | JP2752751B2 (en) |
| CA (1) | CA2032680C (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5495105A (en) * | 1992-02-20 | 1996-02-27 | Canon Kabushiki Kaisha | Method and apparatus for particle manipulation, and measuring apparatus utilizing the same |
| JPH05257085A (en) * | 1992-03-11 | 1993-10-08 | Nikon Corp | Lighting optical system |
| EP0857986B1 (en) | 1996-08-20 | 2006-03-08 | Seiko Epson Corporation | Optical device, polarized light illuminating apparatus and projection-type display |
| JP4966506B2 (en) * | 2005-03-24 | 2012-07-04 | 三洋電機株式会社 | Illumination device and projection display device |
| JP4935089B2 (en) * | 2006-01-30 | 2012-05-23 | 株式会社日立製作所 | Projection-type image display device |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0293580A (en) * | 1988-09-30 | 1990-04-04 | Sony Corp | Image projection device |
| JPH03114027A (en) * | 1989-09-28 | 1991-05-15 | Matsushita Electric Ind Co Ltd | Liquid crystal video projector |
| JP2893599B2 (en) * | 1989-10-05 | 1999-05-24 | セイコーエプソン株式会社 | Polarized light source and projection display |
| JPH03175412A (en) * | 1989-12-05 | 1991-07-30 | Victor Co Of Japan Ltd | Polarization converting element |
-
1989
- 1989-12-20 JP JP1330033A patent/JP2752751B2/en not_active Expired - Fee Related
-
1990
- 1990-12-19 CA CA 2032680 patent/CA2032680C/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| JPH03191318A (en) | 1991-08-21 |
| JP2752751B2 (en) | 1998-05-18 |
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| Date | Code | Title | Description |
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| EEER | Examination request | ||
| MKLA | Lapsed | ||
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Effective date: 20121202 |