CA2234643A1 - Projector - Google Patents
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- CA2234643A1 CA2234643A1 CA002234643A CA2234643A CA2234643A1 CA 2234643 A1 CA2234643 A1 CA 2234643A1 CA 002234643 A CA002234643 A CA 002234643A CA 2234643 A CA2234643 A CA 2234643A CA 2234643 A1 CA2234643 A1 CA 2234643A1
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- Prior art keywords
- light
- polarized
- projector according
- polarizing beam
- splitter
- Prior art date
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- Abandoned
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- 230000010287 polarization Effects 0.000 claims abstract description 33
- 238000003491 array Methods 0.000 claims description 44
- 239000004973 liquid crystal related substance Substances 0.000 claims description 13
- 230000003595 spectral effect Effects 0.000 claims description 4
- 238000011144 upstream manufacturing Methods 0.000 claims description 4
- 230000002708 enhancing effect Effects 0.000 claims description 2
- 230000017525 heat dissipation Effects 0.000 claims description 2
- 239000000306 component Substances 0.000 description 55
- 239000013078 crystal Substances 0.000 description 4
- 206010041662 Splinter Diseases 0.000 description 2
- 230000000712 assembly Effects 0.000 description 2
- 238000000429 assembly Methods 0.000 description 2
- 238000009825 accumulation Methods 0.000 description 1
- 230000002730 additional effect Effects 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 239000003086 colorant Substances 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 229910001507 metal halide Inorganic materials 0.000 description 1
- 150000005309 metal halides Chemical class 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 238000013021 overheating Methods 0.000 description 1
- 230000035515 penetration Effects 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N9/00—Details of colour television systems
- H04N9/12—Picture reproducers
- H04N9/31—Projection devices for colour picture display, e.g. using electronic spatial light modulators [ESLM]
- H04N9/3102—Projection devices for colour picture display, e.g. using electronic spatial light modulators [ESLM] using two-dimensional electronic spatial light modulators
- H04N9/3105—Projection devices for colour picture display, e.g. using electronic spatial light modulators [ESLM] using two-dimensional electronic spatial light modulators for displaying all colours simultaneously, e.g. by using two or more electronic spatial light modulators
- H04N9/3108—Projection devices for colour picture display, e.g. using electronic spatial light modulators [ESLM] using two-dimensional electronic spatial light modulators for displaying all colours simultaneously, e.g. by using two or more electronic spatial light modulators by using a single electronic spatial light modulator
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N9/00—Details of colour television systems
- H04N9/12—Picture reproducers
- H04N9/31—Projection devices for colour picture display, e.g. using electronic spatial light modulators [ESLM]
- H04N9/3141—Constructional details thereof
- H04N9/315—Modulator illumination systems
- H04N9/3167—Modulator illumination systems for polarizing the light beam
Landscapes
- Engineering & Computer Science (AREA)
- Multimedia (AREA)
- Signal Processing (AREA)
- Liquid Crystal (AREA)
- Projection Apparatus (AREA)
Abstract
A projector including a non-polarized light source (10), a polarizing beamsplitter (12) receiving light from the non-polarized light source and a selectably actuatable polarization rotating light valve (16) having light polarized in one sense from the polarizing beam-splitter impinging thereon from a first direction and having light polarized in an opposite sense from the polarizing beam-splitter impinging thereon from a second direction.
Description
CA 02234643 l998-04-l4 - W O 97/14076 - PCT~L96.'~2 f~
PROJECTOR
The present invention relates to projectors.
Various types of video and computer generated information projectors are known. These include, for example, the SharpVision product line commercially avail-able from Sharp Corporation of Japan. Conventional projectors of this type have achieved significant market penetration but suffer from various disadvantages and limitations.
One of the significant limitPtiorls in liquid crystal panel projectors lies in the relatively limited amount of light that can be projected. It may be appreci-ated that the amount of light that can be transmitted through a conventional color liquid crystal panel assem-bly is limited by the amount of light that can be ab-sorbed by the liquid crystal panel without degradation of its performance and permanent damage thereto inter alia mainly due to overheating. Accordingly the bright-ness of projected images produced by such projectors is correspondingly limited.
The present invention seeks to provide an improved projector which is highly efficient in light utilization.
There is thus provided in accordance with a preferred embodiment of the present invention a projector comprising:
a non-polarized light source;
a polarizing beam splitter receiving light from the non-polarized light source; and a selectably actuable polarization rotating light valve having light polarized in one sense from the polarizing beam-splitter impinging thereon from a first direction and having light polarized in an opposite sense from the polarizing beam-splitter impinging thereon from a second direction.
In accordance with a preferred embodiment of CA 02234643 l998-04-l4 - W O 97/14076- PCT/IL96/0~6 the present invention, when the light valve is not actu-ated, the light polarized in both the one sense and the opposite sense passes therethrough without changes in polarization.
Further in accordance with a preferred embodi-ment of the present invention, when the light valve is actuated, the light polarized in both the one sense and the opposite sense passes therethrough with changes in polarization to an extent determined by the actuation.
The range of rotat~on produced by th~ l~ght valve is from Q to 9~ degrees.
Additionally in accordance with a preferred embodiment of the invention, when the light valve is not actuated all of the light is directed to an objective lens.
Still further in accordance with a preferred embodiment of the invention, when the light valve is actuated to cause a 90 degree rotation of the polariza-tion, all of the light is directed back to the light source.
In this manner, very small light losses and heat dissipation is encountered at the light valve, enabling relatively high brightness to be achieved using relatively low power light sources.
Preferably, the light valve is a liguid crystal light valve from which polarization plates have been removed. Preferably the light valve comprises a multi-plicity of independently electrically actuable regions, corresponding to pixels.
In accordance with a preferred embodiment of the present invention, the polarizing beam splitter comprises a pair of prisms which are cemented together with multiple dielectric layers therebetween. In accord-ance with another preferred embodiment of the present invention, the beam splitter is a crystallizing polariz-ing beam splitter. Other suitable types of ~olarizing - - W O 97/14076- PCT~L9~ D06' beam splitters may also be employed.
-~The projector may be monochromati~ or may operate in color. In order to enhance light utilization efficiency when the projector operates in color, prefera-bly, the selectably polarization rotating light valve comprises:
a shutter assembly having a multiplicity of pixel light valves; and a color separator disposed on each side of the shutter assembly, intermediate ~he light sourc~ and the shutter assembly and spaced therefrom and providing a plurality of spatially separated differently colored light beams;
wherein the plurality of spatially separated differently colored light beams are in predetermined registration with the multiplicity of pixel light valves.
Alternatively a color projector may employ three separate monochromatic light sources, polarizing beam splitters and selectably actuable polarization rotating light valves, whose outputs are combined into a single image.
It will be appreciated that the present inven-tion provides greatly enhanced light utilization effi-ciency, which may reach one order of magnitude, as com-pared with prior art devices.
The present invention will be understood and appreciated more fully from the following detailed de-scription, taken in conjunction with the drawings in which:
Fig. 1 is a simplified schematic illustration of a projector constructed and operative in accordance with a preferred embodiment of the present invention;
Figs. 2 and 3 are simplified schematic illus-trations of the passage of two differently polarized components of one ray of light through part of a projec-tor constructed and operative in accordance with a pre-CA 02234643 l998-04-l4 - W O 97/14076 PCT~L9G/0_ '5 ferred embodiment of the present invention in respective first and second operative states;
Fig. 4 is a simplified schematic illustration of a color projector employing three monochromatic subas-semblies in accordance with an alternative embodiment of the present invention;
Fig. 5 is a simplified schematic illustration of a color projector employing three monochromatic subas-semblies in accordance with a further alternative embodi-ment of t~e present invention;
Fig. 6 is a simplified schematic illustration of a color projector employing three monochromatic subas-semblies in accordance with yet another alternative embodiment of the present invention;
Fig. 7 is a simplified schematic illustration of a projector constructed and operative in ~ccordance with another preferred embodiment of the present inven-tion;
Fig. 8 is a simplified schematic illustration of a projector constructed and operative in accordance with yet another preferred embodiment of th~ present invention;
Fig. 9 is a simplified schematic illustration of a color projector constructed and operative in accord-ance with still another preferred embodiment of the present invention;
Fig. 1~ is an illustration of a projector employing two light valve arrays in a reflective mode in accordance with one embodiment of the present invention;
Fig. 11 is an illustration of a projector employing two light valve arrays in accordance with another embodiment of the present invention;
Fig. 12 is an illustration of a projector employing two light valve arraYS in accordance with yet another embodiment of the present invention, which pro-vides enhanced contrast;
CA 02234643 l998-04-l4 - - W O 97/14076 PCT~L~/C~
Fig. 13 is an illustration of a color projec-tor employing two light valve arrays in accordance with still another embodiment of the present invention, which provides enhanced contrast;
Fig. 14 is an illustration of a color projec-tor emploYing two light valve arrays in accordance with a further embodiment of the present invention, which pro-vides enhanced contrast;
Fig. 15 is an illustration of the operation of ~art of the apparatus of Fig. 14;
Fig. 16 is an illustration of a color projec-tor employing two light valve arrays in accordance with a still further embodiment of the present invention; and Fig. 17 is an illustration of the operation of part of the apparatus of Fig. 16.
Reference is now made to Fig. 1, which is a simplified schematic illustration of a projector con-structed and operative in accordance with a preferred embodiment of the present invention. The projector of the present invention comprises a light source 10, such as a metal halide arc lamp manufactured by Osram or Philips combined with a suitable reflector, which outputs a generally collimated beam of light 11 to a ?olarizing beam splitter 12. The polarizing beam splitter may be any suitable polarizing beam splitter and may be similar to, for example, a broadband polarizing cube beam splitter, commercially available from Melles Griot or a crystal polarizer beam splitter, commercially available from Spindler & Hoyer.
According to a preferred embodiment of the present invention, the polarizing beam splitter may be based on a liquid crystal layer disposed betwean a pair of prisms. Such a polarizing beam splitter which is achromatic and has a large acceptance angle, is commercially available from Philips Key Modules Group, Building SWA 8, 56Q~ JB Eindhoven, the Netherlands.
W 0 97/14076 PCT~L~ ~ 5 Although a prism-type beam splitter is illus-trated throughout, it is appreciated that a planar type beam splitter is equally applicable.
The operation of the apparatus of Fig. 1 may be best appreciated by a consideration of a number of indi-vidual differently polarized components of individual rays of light forming beam 11 together with a considera-tion of Figs. 2 and 3, which show the passage of the differently polarized components of individual rays of light separately through respsctive actuated and non-actuated pixels of the light valve array.
A first polarized component of a ray of light, represented by a solid line, and labeled ls, is reflected by the polarizing beam splitter 12 via a mirror 14 to impinge upon a light valve array 16 in a first direc-tion, indicated by arrows 18. A second polariz~d compo-nent of the same ray of light, polarized orthog~nally to the first polarized component of light represented by a dashed line and labeled lp, passes through beam splitter 12 and is reflected from a mirror 2~ to impinge upon light valve array 16 in a second direction, indicated by arrows 22.
The light valve array 16 may be any suitable light valve array and is preferably a liquid crystal light valve array from which the polarization plates thereof have been removed. The liquid crystal light valve array may be monochromatic but is preferably a color array. A preferred embodiment of a color liquid crystal light valve array is described and clAimed in applicant/assignee's Published European Patent Applica-tion ~631434.
If it is desired to employ commercially avail-able off-the-shelf liquid crystal light valves which are normally aligned at 45 degrees with respect to their frames, it is necessary to rotate such liqui~ crystal light valves in their respective planes about the optical - -WO g7/14076 PCT/IL~f~/OCAf' axis of the system by 45 degrees, such that the resulting polarization will coincide with either the s or the p polarized beam components. It is appreciated tllat using conventional technology liquid crystal light valves which are aligned parallel to the rows or columns therein may be used for the purposes of the present invention.
When commercially available off-the-shelf liquid crystal light valves are employed, they ~re opera-tive to transmit light in the absence of the application of an electrical vQltage thereto. This is known as opera-tion in a normally white mode, as distinguished from operation in a normally black mode, when the light valves are opaque in the absence of the application of an elec-trical voltage thereto.
In the apparatus of the present invention, liquid crystal light valves which are designed to operate in the normally white mode would have the opposite effect and block transmission of light. Accordingly, convention-al off-the-shelf li~uid crystal light valves should be operated in an electrically inverse mode or an additional 9~ degree polarization rotator should be employed.
Each pixel in the liquid crystal light valve array may be independently electrically controlled to selectably rotate the polarization of light passing therethrough. The selectable polarization cause3 rotation of light passing therethrough in a range of ~ to 9~
degrees. For the purpose of simplicity in ilLustration and explanation, only two operative states of the light valve array are here considered, namely ~ degrees rota-tion and 9~ degrees rotation, it being understood that grey scales may be expressed by intermediate anounts of rotation.
Returning to a consideration of Fig. 1 and of components ls and lp, it is seen that they bot~ impinge on a pixel which is hatched to indicate 9~ degree rota-tion. Thus the ls component is converted at the light CA 02234643 l998-04-l4 - - W O 97/14076 PCT~L96i~6 valve to a lp' component and the lp component is convert-ed to a ls' component. The resulting lp' component is reflected by mirror 2~ to pass through beam splitter 12 to the light source 10. The resulting ls' component is reflected by mirror 14 and is reflected at beam splitter 12 to the light source 1~. Thus it is seen that both differently polarized components of a beam which impinges on an actuated pixel of the light valve array 16 are eventually reflected back to the light source.
Turning to a consideration of a second light ray having mutually orthogonally polarized components 2s and 2p, it is seen that first polarized component 2s, is reflected by the polarizing beam splitter 12 via mirror 14 to impinge upon light valve array 16 in the first direction, indicated by arrows 18. The second polarized component of the same ray of light, polarized orthogonal-ly to the first polarized component of light represented by a dashed line and labeled 2p, passes through beam splitter 12 and is reflected from mirror 2~ to impinge upon light valve array 16 in a second direction, indicat-ed by arrows 22.
Both differently polarized components impinge on a pixel which is blank to indicate ~ degree rotation.
Thus the 2s component is not converted at the light valve and remains a 2s' component and the 2p component is also not converted and remains a 2p' component. The 2p' component is reflected by mirror 14 to pass through beam splitter 12 to the objective lens 24. The 2s' component is reflected by mirror 2~ and is reflected at beam split-ter 12 to the objective lens 24. Thus it is seen that both differently polarized components of a beam which impinges on an non-actuated pixel of the light valve array 16 are eventually directed to the objective lens.
It is noted that the light valve array 16 should be placed optically equidistant from the objective lens along the light paths of both the p and the s components, - -W O 97/14076 - PCT~L9~
such that the objective lens 24 equally images both sides of the light valve array.
It may be appreciated that in the arrangement of the present invention. depending on the image defined by the polarization states of the various pixels the light is directed either through an objective lens 24 or reflected back to the light source 10, where it may be used to heat the plasma therein, or alternatively be redirected through the projector. Accordingly the heat accumulation at the light valve array due to ligh~ ab-sorption thereat is minimized.
It is a particular feature of the present invention that light of different polarization impinges on the light valve array 16 simultaneously in opposite directions. It is also a particular feature of the present invention that the light impinges upon through the beam splitter twice in every case. These features enable light of both polarizations to contribute to the brightness of an illuminated pixel.
The embodiments described hereinabove may be either monochromatic or color depending on whether color filtration is provided.
Reference is now made to Fig. 4, which illus-trates an embodiment of a color projector. Here three generally identical monochromatic color subassemblies, labeled respectively 4~, 42 and 44 and each including a polarizing beam splitter 12 and a monochromatic light valve array 16, receive light via dichroic beam splitters 46 from a polychromatic light source 48 which may be identical with light source 1~ described hereinabove.
Each of the subassemblies may be constructed and operative as described hereinabove with reference to Figs. 1 - 3. The outputs of light downstream of the light valve arrays 16 pass through the respective beam split-ters 12 of each subassembly and are reflected by mirrors 5~ so as to direct the light via dichroic beam combiners CA 02234643 l998-04-l4 - -W O 97/14076 - PCT~L9 G/~ O S ~S
1 (~) 52, and through a single objective lens 54.
Reference is now made to Fig. 5, whi-h illus-trates a further alternative embodiment of a color projector. Here light from a light source 6~ passes through a polarizing beam splitter 62. The resulting two mutually orthogonally polarized components of the light are directed to respective dichroic beam splitt~-rs 64 and 65.
The red, green and blue components are directed by respecti~7e mirror p~irs 66, 68; 7(), 72 and 74. 76 through three respective monochromatic light valve arrays 78, 8(~ and 82. Light which has passed through one of the three light valve arrays 78, 8~) and 82 is reco:nbined at beam splitter 62 and directed via an objective lens 84 to provide an image output.
Each of the subassemblies may be constructed and operative as described hereinabove with reference to Figs. 1 - 3.
Reference is now made to Fig. 6, which illus-trates a color projector employing three monochromatic subassemblies in accordance with yet another alternative embodiment of the present invention. Here a light source 9~ emits a light beam which impinges on a dichroic beam splitter 92. Blue light reflected therefrom impinges on a polarizing beam splitter 94. The resulting two mutually orthogonally polarized components of the blue light are directed by respective mirrors 96 and 98 via a light valve array 99 and via polarizing beam splitter 94 which directs them to a dichroic beam combiner 1~. Beam combiner l~Q directs the blue light through an objective lens 11~)2.
The red and green components are transmitted through dichroic beam splitter 92 and impinge on a fur-ther dichroic beam splitter lQ4. The green component is transmitted therethrough and impinges on a polarizing beam splitter 1()6. The resulting two mutually orthogonal-CA 02234643 l998-04-l4 - -W O 97/14076 PCT~L9Ç~
ly polarized components of the green light are directed by respective mirrors 1~8 and llQ via a light valve array 111 and via polarizing beam splitter lQ6 which directs them to dichroic beam combiner 1~0, which transmit the green light through objective lens lQ2.
The red component is reflected by the dichroic beam splitter 1~4 onto a mirror 114 which directs it to a mirror 116, which reflects it onto a polarizing beam splitter 118. The resulting two mutually orthogonally polarized components of the red light are directed by respective mirrors 12~ and 122 via a light valve array 123 and via polarizing beam splitter 118 which directs them to dichroic beam combiner 1~, which directs the red light through objective lens 1~2.
Reference is now made to Fig. 7, which illus-trates a projector constructed and operative in accord-ance with another preferred embodiment of the present invention. The projector of Fig. 7 may be identical to that of Fig. 1, with the additional feature that one or both of mirrors 214 and 22~ may be adjustably position-able, dynamically or statically by alignment apparatus 221 and 215 respectively. The remaining elements of the structure are indicated by identical reference numerals.
By using the adjustably positionable nirror or mirrors 214 and 220 one may cause two slightly mutually translated images of a pattern on the light valve array 16 to be projected via objective lens 24. This may pro-duce depixelization of the resulting image, which is desirable in certain applications, such as video dis-plays.
Fig. 8 illustrates the apparatus of Fig. 7 with the addition of apparatus for dynamically varying the position of mirrors 214 and 22~. This apparatus may include, for example, piezoelectric assemblies 222 and 224, as illustrated in Fig. 8. By using the appPratus of Fig. 8, one may produce interlaced image fields and thus CA 02234643 l998-04-l4 - - W O97/14076- PCT~L9G~
achieve enhanced image resolution, which may double or triple the number of rows per image without adding addi-tional resolution requirements to the remainder of the apparatus, provided that the frame rate of the light valve array 16 is sufficiently high.
Reference is now made to Fig. 9, which illus-trates a color projector constructed and operative in accordance with a preferred embodiment of the present invention. A light source 25t~) projects a beam of light via a color wheel 252 or any o~her suitable device for sequentially transmitting the R, G and B spectral compo-nents of the beam, onto a polarizing beam splitter 254.
The resulting two mutually orthogonally polarizod compo-nents of the R, G and B spectral components are directed by respective mirrors 256 and 258 via a light valve array 26() and via polarizing beam splitter 254 which directs them through an objective lens 262.
Reference is now made to Fig. 10, which illus-trates a projector employing two light valve arrays in a reflective mode. Light from a light source 27(~) impinges on a polarizing beam splitter 272. The resulting two mutually orthogonally polarized components of the light are directed via two separate light valve arrays 274 and 276 and respective ~uarter wave plates 278 and 28(~ to respective mirrors 282 and 284. The light is reflected back via respective guarter wave plates 278 and 28() and light valve arrays 274 and 276 to polarizing beam split-ter 272 and is directed thereby through an objective lens 286.
The light valve arrays 274 and 276 both operate in a reflective mode. It is noted that the light valve arrays 274 and 276 do not include polarizers.
As in the embodiments of Figs. 7 and 8, by slightly translating either of the light valve arrays 274 and 276 along respective arrows 2gt) and 292 or perpen-dicularly thereto in the same plane one may cause two CA 02234643 l998-04-l4 - - W O 97/14076 PCT~L96/~CC65 slightly mutually translated superimposed images of patterns on the light valve arrays to be projected via objective lens 286. When identical images appear on both light valve arrays 274 and 276, this may produce depixe-lization of the resulting image, which is desirable in certain applications, such as video displays. When dif-ferent fields appear on the two light valve arrays, doubled image resolution in both mutually orthogonal directions may result.
By translating one or both of t~e ligh~ valve arrays 274 and 276 dynamically, analogously to the embod-iment of Fig. 8, even greater increases in resolution can be achieved.
It is appreciated that in all of thP embodi-ments employing two light valve arrays, the light valve arrays should be placed optically equidistant from the objective lens.
Reference is now made to Fig. 11, which is an illustration of a projector employing two light valve arrays in accordance with another embodiment of the present invention.
Light from a light source 3t)~) impinges on a polarizing beam splitter 302. The resulting two mutually orthogonally polarized components of the light p and s are directed via two separate mirrors 3~4 and 3~6 and respective light valve arrays 3(~8 and 31~) to a polarizing beam splitter 312.
When a voltage is not applied to light valve arrays 3(~)8 and 31(), all of the light impinging on polar-izing beam splitter 312 is directed to an objective lens . 314, for operation in a normally white mode. When a voltage is applied to light valve arrays 3(~)8 and 31(~), some or all of the light impinging on polarizing beam splitter 312 iS directed in a direction indicated by an arrow 316. If it is desired to operate in a normally black mode, an objective lens 318 may be provided to - - W O 97/14076 - PCT~L96/00065 focus light directed along arrow 316 and to provide an image thereof.
As in the embodiments of Figs. 7 and 8, by slightly translating either of the light valve arrays 3~8 and 31~ along respective arrows 32~ and 322 or perpen-dicularly thereto in the same plane, one may cause two slightly mutually translated superimposed images of patterns on the light valve arrays to be projected via the objective lens. When identical images appear on both light valve arrays 3~8 and 31~, th~s may produce depixe-lization of the resulting image, which is desirable in certain applications, such as video displays. rAhen dif-ferent fields appear on the two light valve arrays, doubled image resolution in both mutually orthogonal directions may result.
By translating one or both of the light valve arrays 3~8 and 31~ dynamically, analogously to the embod-iment of Fig. 8, even greater increases in resolution can be achieved.
It is appreciated that light valve arrays 3~8 and 31~ may be monochromatic or polychromatic. Where the light valve arrays 3~8 or 31~ are monochromatic, a poly-chromatic projector may be realized by combining suitably filtered light passing through three parallel devices of the type illustrated in Fig. 11.
Reference is now made to Fig. 12, which is an illustration of a projector employing two light valve arrays in accordance with yet another embodiment of the present invention, which provides enhanced contrast. The embodiment of Fig. 12 may be identical to that of Fig. 11 and identical elements are shown by the same reference numerals, with the following exception:
Mirror 3~6 is replaced by a polarizing beam splitter 33~ which directs the s polarized component via light valve array 31~ as in the embodiment of Fig. 11. In accordance with a preferred embodiment of the invention, CA 02234643 l998-04-l4 - W O 97114076 PCT~L9C~
the polarizing beam splitter 33(3 is also effective to filter out a residual p component which impinges thereon together with the s component, and directs it in a direc-tion indicated by an arrow 332, thus removing it from the system and thus enhancing contrast.
Reference is now made to Fig. 13, which is an illustration of a color projector employing two light valve arrays in accordance with still another embodiment of the present invention, which provides enhanced con-trast. The embodiment oP Fig. 13 may be identic:~l to that of' Fig. 12 and identical elements are shown by the same reference numerals, with the following exception:
A color wheel 34~ or any other suitable device for sequentially transmitting the R, G and B spectral components of the beam is located intermediate the light source 3~)() and the polarizing beam splitter 302. This arrangement can be employed with particular utility when the light valve arrays 3~)8 and 31() are monochromatic, for providing a color projector.
Reference is now made to Fig. 14, which is an illustration of a color projector employing two light valve arrays in accordance with a further embodiment of the present invention, which provides enhanced contrast.
The embodiment of Fig. 14 may be identical to that of Fig. 12 and identical elements are shown by the same reference numerals, with the following exception:
In order to provide greatly enhanced light utilization at the light valves 3(~8 and 31(~), prism/lens combination arrays 35O and 352 are disposed upstream of respective light valve arrays 3O8 and 311~). The prism/lens ~ combination arrays 35~ and 352 may be of the type de-scribed and claimed in applicant/assignee's Published European Patent Application ~)631434.
As seen in Fig. 15, each component of an incom-ing collimated ray of light 354 is broken down by the prism/lens array 35~) into bands of different colors, CA 02234643 l998-04-l4 - - W 097/14076 - PCT~L9G/~ 5 each of which passes through a separate pixel in light valve 3~)8. This arrangement has substantial benefits in terms of light utilization efficiency as described in applicant/assignee's Published European Patent Applica-tion (~)6331434, the disclosure of which is hereby incorpo-rated by reference.
Reference is now made to Fig. 16, which is an illustration of a color projector employing two light valve arrays in accordance with still another ~mbodiment of the present invention. The embodiment of Fig. 16 may be identical to that of Fig. 11 and identical elements are shown by the same reference numerals, with the fol-lowing exception:
In order to provide greatly enhanced light utilization at the light valves 3(~)8 and 31(~), there are provided in front of mirror 3t~4 a pair of slightly tilted dichroic reflectors 360 and 362. Mirror 304 and dichroic reflectors 36(~ and 362 are together operative to provide a fan of the separate R, G and B components of light, each component being angularly separated from the other.
Similarly, there are provided in front of mirror 3(~)6 a pair of slightly tilted dichroic reflectors 364 and 366. Mirror 3t)6 and dichroic reflectors 364 and 366 are together operative to provide a fan of the sepa-rate R, G and B components of light, each component being angularly separated from the other.
The three mutually angularly separated compo-nents R, G and B impinge on respective lens arrays 368 and 37(~), which are disposed upstream of respective light valve arrays 308 and 310.
As seen in Fig. 17, each of the R, G and B
components of an incoming collimated ray of light 38(~) is focused by the lens array 368 through a separ~te pixel in light valve 3t~)8. This arrangement has substantial benefits in terms of light utilization efficiency as described in applicant/assignee's Published European CA 02234643 l998-04-l4 - W O 97/14076 PCT~L96,~~0CC
Patent Application 06331434, the disclosure of which is hereby incorporated by reference.
It is appreciated that the embodiments of Figs.
17 may be employed to provide stereo projection without the need for plural projectors. Reference is made, for example, to the embodiment of Fig. 11, wherein light valve arrays 3~8 and 31~ each represent information to be presented to a separate eye of a viewer, who wears conventional passive polarized eyeglasses. The lnformation to be presented to the left eye is provided, for example, by light valve array 3~8 with a vertical polarization and the information to be presented to the right eye is provided, for example, by light valve array 31~ with a horizontal polarization. The passive polarized eyeglasses in such a case would have vertical polarization in front of the left eye and horizontal polarization in front of the right eye.
It is appreciated that for simplicity and conciseness of description, not all of the standard components of a projector have been specifically de-scribed herein. These components include IR an~ UV fil-ters and fresnel lenses. It is to be understood that all conventional components of a projector are assumed to be - included in the projectors of the present invention even though they are not specifically mentioned herein.
It will be appreciated by persons s~illed in the art that the present invention is not limited by what has been particularly shown and described hereinabove.
Rather the scope of the present invention is defined only by the claims which follow:
PROJECTOR
The present invention relates to projectors.
Various types of video and computer generated information projectors are known. These include, for example, the SharpVision product line commercially avail-able from Sharp Corporation of Japan. Conventional projectors of this type have achieved significant market penetration but suffer from various disadvantages and limitations.
One of the significant limitPtiorls in liquid crystal panel projectors lies in the relatively limited amount of light that can be projected. It may be appreci-ated that the amount of light that can be transmitted through a conventional color liquid crystal panel assem-bly is limited by the amount of light that can be ab-sorbed by the liquid crystal panel without degradation of its performance and permanent damage thereto inter alia mainly due to overheating. Accordingly the bright-ness of projected images produced by such projectors is correspondingly limited.
The present invention seeks to provide an improved projector which is highly efficient in light utilization.
There is thus provided in accordance with a preferred embodiment of the present invention a projector comprising:
a non-polarized light source;
a polarizing beam splitter receiving light from the non-polarized light source; and a selectably actuable polarization rotating light valve having light polarized in one sense from the polarizing beam-splitter impinging thereon from a first direction and having light polarized in an opposite sense from the polarizing beam-splitter impinging thereon from a second direction.
In accordance with a preferred embodiment of CA 02234643 l998-04-l4 - W O 97/14076- PCT/IL96/0~6 the present invention, when the light valve is not actu-ated, the light polarized in both the one sense and the opposite sense passes therethrough without changes in polarization.
Further in accordance with a preferred embodi-ment of the present invention, when the light valve is actuated, the light polarized in both the one sense and the opposite sense passes therethrough with changes in polarization to an extent determined by the actuation.
The range of rotat~on produced by th~ l~ght valve is from Q to 9~ degrees.
Additionally in accordance with a preferred embodiment of the invention, when the light valve is not actuated all of the light is directed to an objective lens.
Still further in accordance with a preferred embodiment of the invention, when the light valve is actuated to cause a 90 degree rotation of the polariza-tion, all of the light is directed back to the light source.
In this manner, very small light losses and heat dissipation is encountered at the light valve, enabling relatively high brightness to be achieved using relatively low power light sources.
Preferably, the light valve is a liguid crystal light valve from which polarization plates have been removed. Preferably the light valve comprises a multi-plicity of independently electrically actuable regions, corresponding to pixels.
In accordance with a preferred embodiment of the present invention, the polarizing beam splitter comprises a pair of prisms which are cemented together with multiple dielectric layers therebetween. In accord-ance with another preferred embodiment of the present invention, the beam splitter is a crystallizing polariz-ing beam splitter. Other suitable types of ~olarizing - - W O 97/14076- PCT~L9~ D06' beam splitters may also be employed.
-~The projector may be monochromati~ or may operate in color. In order to enhance light utilization efficiency when the projector operates in color, prefera-bly, the selectably polarization rotating light valve comprises:
a shutter assembly having a multiplicity of pixel light valves; and a color separator disposed on each side of the shutter assembly, intermediate ~he light sourc~ and the shutter assembly and spaced therefrom and providing a plurality of spatially separated differently colored light beams;
wherein the plurality of spatially separated differently colored light beams are in predetermined registration with the multiplicity of pixel light valves.
Alternatively a color projector may employ three separate monochromatic light sources, polarizing beam splitters and selectably actuable polarization rotating light valves, whose outputs are combined into a single image.
It will be appreciated that the present inven-tion provides greatly enhanced light utilization effi-ciency, which may reach one order of magnitude, as com-pared with prior art devices.
The present invention will be understood and appreciated more fully from the following detailed de-scription, taken in conjunction with the drawings in which:
Fig. 1 is a simplified schematic illustration of a projector constructed and operative in accordance with a preferred embodiment of the present invention;
Figs. 2 and 3 are simplified schematic illus-trations of the passage of two differently polarized components of one ray of light through part of a projec-tor constructed and operative in accordance with a pre-CA 02234643 l998-04-l4 - W O 97/14076 PCT~L9G/0_ '5 ferred embodiment of the present invention in respective first and second operative states;
Fig. 4 is a simplified schematic illustration of a color projector employing three monochromatic subas-semblies in accordance with an alternative embodiment of the present invention;
Fig. 5 is a simplified schematic illustration of a color projector employing three monochromatic subas-semblies in accordance with a further alternative embodi-ment of t~e present invention;
Fig. 6 is a simplified schematic illustration of a color projector employing three monochromatic subas-semblies in accordance with yet another alternative embodiment of the present invention;
Fig. 7 is a simplified schematic illustration of a projector constructed and operative in ~ccordance with another preferred embodiment of the present inven-tion;
Fig. 8 is a simplified schematic illustration of a projector constructed and operative in accordance with yet another preferred embodiment of th~ present invention;
Fig. 9 is a simplified schematic illustration of a color projector constructed and operative in accord-ance with still another preferred embodiment of the present invention;
Fig. 1~ is an illustration of a projector employing two light valve arrays in a reflective mode in accordance with one embodiment of the present invention;
Fig. 11 is an illustration of a projector employing two light valve arrays in accordance with another embodiment of the present invention;
Fig. 12 is an illustration of a projector employing two light valve arraYS in accordance with yet another embodiment of the present invention, which pro-vides enhanced contrast;
CA 02234643 l998-04-l4 - - W O 97/14076 PCT~L~/C~
Fig. 13 is an illustration of a color projec-tor employing two light valve arrays in accordance with still another embodiment of the present invention, which provides enhanced contrast;
Fig. 14 is an illustration of a color projec-tor emploYing two light valve arrays in accordance with a further embodiment of the present invention, which pro-vides enhanced contrast;
Fig. 15 is an illustration of the operation of ~art of the apparatus of Fig. 14;
Fig. 16 is an illustration of a color projec-tor employing two light valve arrays in accordance with a still further embodiment of the present invention; and Fig. 17 is an illustration of the operation of part of the apparatus of Fig. 16.
Reference is now made to Fig. 1, which is a simplified schematic illustration of a projector con-structed and operative in accordance with a preferred embodiment of the present invention. The projector of the present invention comprises a light source 10, such as a metal halide arc lamp manufactured by Osram or Philips combined with a suitable reflector, which outputs a generally collimated beam of light 11 to a ?olarizing beam splitter 12. The polarizing beam splitter may be any suitable polarizing beam splitter and may be similar to, for example, a broadband polarizing cube beam splitter, commercially available from Melles Griot or a crystal polarizer beam splitter, commercially available from Spindler & Hoyer.
According to a preferred embodiment of the present invention, the polarizing beam splitter may be based on a liquid crystal layer disposed betwean a pair of prisms. Such a polarizing beam splitter which is achromatic and has a large acceptance angle, is commercially available from Philips Key Modules Group, Building SWA 8, 56Q~ JB Eindhoven, the Netherlands.
W 0 97/14076 PCT~L~ ~ 5 Although a prism-type beam splitter is illus-trated throughout, it is appreciated that a planar type beam splitter is equally applicable.
The operation of the apparatus of Fig. 1 may be best appreciated by a consideration of a number of indi-vidual differently polarized components of individual rays of light forming beam 11 together with a considera-tion of Figs. 2 and 3, which show the passage of the differently polarized components of individual rays of light separately through respsctive actuated and non-actuated pixels of the light valve array.
A first polarized component of a ray of light, represented by a solid line, and labeled ls, is reflected by the polarizing beam splitter 12 via a mirror 14 to impinge upon a light valve array 16 in a first direc-tion, indicated by arrows 18. A second polariz~d compo-nent of the same ray of light, polarized orthog~nally to the first polarized component of light represented by a dashed line and labeled lp, passes through beam splitter 12 and is reflected from a mirror 2~ to impinge upon light valve array 16 in a second direction, indicated by arrows 22.
The light valve array 16 may be any suitable light valve array and is preferably a liquid crystal light valve array from which the polarization plates thereof have been removed. The liquid crystal light valve array may be monochromatic but is preferably a color array. A preferred embodiment of a color liquid crystal light valve array is described and clAimed in applicant/assignee's Published European Patent Applica-tion ~631434.
If it is desired to employ commercially avail-able off-the-shelf liquid crystal light valves which are normally aligned at 45 degrees with respect to their frames, it is necessary to rotate such liqui~ crystal light valves in their respective planes about the optical - -WO g7/14076 PCT/IL~f~/OCAf' axis of the system by 45 degrees, such that the resulting polarization will coincide with either the s or the p polarized beam components. It is appreciated tllat using conventional technology liquid crystal light valves which are aligned parallel to the rows or columns therein may be used for the purposes of the present invention.
When commercially available off-the-shelf liquid crystal light valves are employed, they ~re opera-tive to transmit light in the absence of the application of an electrical vQltage thereto. This is known as opera-tion in a normally white mode, as distinguished from operation in a normally black mode, when the light valves are opaque in the absence of the application of an elec-trical voltage thereto.
In the apparatus of the present invention, liquid crystal light valves which are designed to operate in the normally white mode would have the opposite effect and block transmission of light. Accordingly, convention-al off-the-shelf li~uid crystal light valves should be operated in an electrically inverse mode or an additional 9~ degree polarization rotator should be employed.
Each pixel in the liquid crystal light valve array may be independently electrically controlled to selectably rotate the polarization of light passing therethrough. The selectable polarization cause3 rotation of light passing therethrough in a range of ~ to 9~
degrees. For the purpose of simplicity in ilLustration and explanation, only two operative states of the light valve array are here considered, namely ~ degrees rota-tion and 9~ degrees rotation, it being understood that grey scales may be expressed by intermediate anounts of rotation.
Returning to a consideration of Fig. 1 and of components ls and lp, it is seen that they bot~ impinge on a pixel which is hatched to indicate 9~ degree rota-tion. Thus the ls component is converted at the light CA 02234643 l998-04-l4 - - W O 97/14076 PCT~L96i~6 valve to a lp' component and the lp component is convert-ed to a ls' component. The resulting lp' component is reflected by mirror 2~ to pass through beam splitter 12 to the light source 10. The resulting ls' component is reflected by mirror 14 and is reflected at beam splitter 12 to the light source 1~. Thus it is seen that both differently polarized components of a beam which impinges on an actuated pixel of the light valve array 16 are eventually reflected back to the light source.
Turning to a consideration of a second light ray having mutually orthogonally polarized components 2s and 2p, it is seen that first polarized component 2s, is reflected by the polarizing beam splitter 12 via mirror 14 to impinge upon light valve array 16 in the first direction, indicated by arrows 18. The second polarized component of the same ray of light, polarized orthogonal-ly to the first polarized component of light represented by a dashed line and labeled 2p, passes through beam splitter 12 and is reflected from mirror 2~ to impinge upon light valve array 16 in a second direction, indicat-ed by arrows 22.
Both differently polarized components impinge on a pixel which is blank to indicate ~ degree rotation.
Thus the 2s component is not converted at the light valve and remains a 2s' component and the 2p component is also not converted and remains a 2p' component. The 2p' component is reflected by mirror 14 to pass through beam splitter 12 to the objective lens 24. The 2s' component is reflected by mirror 2~ and is reflected at beam split-ter 12 to the objective lens 24. Thus it is seen that both differently polarized components of a beam which impinges on an non-actuated pixel of the light valve array 16 are eventually directed to the objective lens.
It is noted that the light valve array 16 should be placed optically equidistant from the objective lens along the light paths of both the p and the s components, - -W O 97/14076 - PCT~L9~
such that the objective lens 24 equally images both sides of the light valve array.
It may be appreciated that in the arrangement of the present invention. depending on the image defined by the polarization states of the various pixels the light is directed either through an objective lens 24 or reflected back to the light source 10, where it may be used to heat the plasma therein, or alternatively be redirected through the projector. Accordingly the heat accumulation at the light valve array due to ligh~ ab-sorption thereat is minimized.
It is a particular feature of the present invention that light of different polarization impinges on the light valve array 16 simultaneously in opposite directions. It is also a particular feature of the present invention that the light impinges upon through the beam splitter twice in every case. These features enable light of both polarizations to contribute to the brightness of an illuminated pixel.
The embodiments described hereinabove may be either monochromatic or color depending on whether color filtration is provided.
Reference is now made to Fig. 4, which illus-trates an embodiment of a color projector. Here three generally identical monochromatic color subassemblies, labeled respectively 4~, 42 and 44 and each including a polarizing beam splitter 12 and a monochromatic light valve array 16, receive light via dichroic beam splitters 46 from a polychromatic light source 48 which may be identical with light source 1~ described hereinabove.
Each of the subassemblies may be constructed and operative as described hereinabove with reference to Figs. 1 - 3. The outputs of light downstream of the light valve arrays 16 pass through the respective beam split-ters 12 of each subassembly and are reflected by mirrors 5~ so as to direct the light via dichroic beam combiners CA 02234643 l998-04-l4 - -W O 97/14076 - PCT~L9 G/~ O S ~S
1 (~) 52, and through a single objective lens 54.
Reference is now made to Fig. 5, whi-h illus-trates a further alternative embodiment of a color projector. Here light from a light source 6~ passes through a polarizing beam splitter 62. The resulting two mutually orthogonally polarized components of the light are directed to respective dichroic beam splitt~-rs 64 and 65.
The red, green and blue components are directed by respecti~7e mirror p~irs 66, 68; 7(), 72 and 74. 76 through three respective monochromatic light valve arrays 78, 8(~ and 82. Light which has passed through one of the three light valve arrays 78, 8~) and 82 is reco:nbined at beam splitter 62 and directed via an objective lens 84 to provide an image output.
Each of the subassemblies may be constructed and operative as described hereinabove with reference to Figs. 1 - 3.
Reference is now made to Fig. 6, which illus-trates a color projector employing three monochromatic subassemblies in accordance with yet another alternative embodiment of the present invention. Here a light source 9~ emits a light beam which impinges on a dichroic beam splitter 92. Blue light reflected therefrom impinges on a polarizing beam splitter 94. The resulting two mutually orthogonally polarized components of the blue light are directed by respective mirrors 96 and 98 via a light valve array 99 and via polarizing beam splitter 94 which directs them to a dichroic beam combiner 1~. Beam combiner l~Q directs the blue light through an objective lens 11~)2.
The red and green components are transmitted through dichroic beam splitter 92 and impinge on a fur-ther dichroic beam splitter lQ4. The green component is transmitted therethrough and impinges on a polarizing beam splitter 1()6. The resulting two mutually orthogonal-CA 02234643 l998-04-l4 - -W O 97/14076 PCT~L9Ç~
ly polarized components of the green light are directed by respective mirrors 1~8 and llQ via a light valve array 111 and via polarizing beam splitter lQ6 which directs them to dichroic beam combiner 1~0, which transmit the green light through objective lens lQ2.
The red component is reflected by the dichroic beam splitter 1~4 onto a mirror 114 which directs it to a mirror 116, which reflects it onto a polarizing beam splitter 118. The resulting two mutually orthogonally polarized components of the red light are directed by respective mirrors 12~ and 122 via a light valve array 123 and via polarizing beam splitter 118 which directs them to dichroic beam combiner 1~, which directs the red light through objective lens 1~2.
Reference is now made to Fig. 7, which illus-trates a projector constructed and operative in accord-ance with another preferred embodiment of the present invention. The projector of Fig. 7 may be identical to that of Fig. 1, with the additional feature that one or both of mirrors 214 and 22~ may be adjustably position-able, dynamically or statically by alignment apparatus 221 and 215 respectively. The remaining elements of the structure are indicated by identical reference numerals.
By using the adjustably positionable nirror or mirrors 214 and 220 one may cause two slightly mutually translated images of a pattern on the light valve array 16 to be projected via objective lens 24. This may pro-duce depixelization of the resulting image, which is desirable in certain applications, such as video dis-plays.
Fig. 8 illustrates the apparatus of Fig. 7 with the addition of apparatus for dynamically varying the position of mirrors 214 and 22~. This apparatus may include, for example, piezoelectric assemblies 222 and 224, as illustrated in Fig. 8. By using the appPratus of Fig. 8, one may produce interlaced image fields and thus CA 02234643 l998-04-l4 - - W O97/14076- PCT~L9G~
achieve enhanced image resolution, which may double or triple the number of rows per image without adding addi-tional resolution requirements to the remainder of the apparatus, provided that the frame rate of the light valve array 16 is sufficiently high.
Reference is now made to Fig. 9, which illus-trates a color projector constructed and operative in accordance with a preferred embodiment of the present invention. A light source 25t~) projects a beam of light via a color wheel 252 or any o~her suitable device for sequentially transmitting the R, G and B spectral compo-nents of the beam, onto a polarizing beam splitter 254.
The resulting two mutually orthogonally polarizod compo-nents of the R, G and B spectral components are directed by respective mirrors 256 and 258 via a light valve array 26() and via polarizing beam splitter 254 which directs them through an objective lens 262.
Reference is now made to Fig. 10, which illus-trates a projector employing two light valve arrays in a reflective mode. Light from a light source 27(~) impinges on a polarizing beam splitter 272. The resulting two mutually orthogonally polarized components of the light are directed via two separate light valve arrays 274 and 276 and respective ~uarter wave plates 278 and 28(~ to respective mirrors 282 and 284. The light is reflected back via respective guarter wave plates 278 and 28() and light valve arrays 274 and 276 to polarizing beam split-ter 272 and is directed thereby through an objective lens 286.
The light valve arrays 274 and 276 both operate in a reflective mode. It is noted that the light valve arrays 274 and 276 do not include polarizers.
As in the embodiments of Figs. 7 and 8, by slightly translating either of the light valve arrays 274 and 276 along respective arrows 2gt) and 292 or perpen-dicularly thereto in the same plane one may cause two CA 02234643 l998-04-l4 - - W O 97/14076 PCT~L96/~CC65 slightly mutually translated superimposed images of patterns on the light valve arrays to be projected via objective lens 286. When identical images appear on both light valve arrays 274 and 276, this may produce depixe-lization of the resulting image, which is desirable in certain applications, such as video displays. When dif-ferent fields appear on the two light valve arrays, doubled image resolution in both mutually orthogonal directions may result.
By translating one or both of t~e ligh~ valve arrays 274 and 276 dynamically, analogously to the embod-iment of Fig. 8, even greater increases in resolution can be achieved.
It is appreciated that in all of thP embodi-ments employing two light valve arrays, the light valve arrays should be placed optically equidistant from the objective lens.
Reference is now made to Fig. 11, which is an illustration of a projector employing two light valve arrays in accordance with another embodiment of the present invention.
Light from a light source 3t)~) impinges on a polarizing beam splitter 302. The resulting two mutually orthogonally polarized components of the light p and s are directed via two separate mirrors 3~4 and 3~6 and respective light valve arrays 3(~8 and 31~) to a polarizing beam splitter 312.
When a voltage is not applied to light valve arrays 3(~)8 and 31(), all of the light impinging on polar-izing beam splitter 312 is directed to an objective lens . 314, for operation in a normally white mode. When a voltage is applied to light valve arrays 3(~)8 and 31(~), some or all of the light impinging on polarizing beam splitter 312 iS directed in a direction indicated by an arrow 316. If it is desired to operate in a normally black mode, an objective lens 318 may be provided to - - W O 97/14076 - PCT~L96/00065 focus light directed along arrow 316 and to provide an image thereof.
As in the embodiments of Figs. 7 and 8, by slightly translating either of the light valve arrays 3~8 and 31~ along respective arrows 32~ and 322 or perpen-dicularly thereto in the same plane, one may cause two slightly mutually translated superimposed images of patterns on the light valve arrays to be projected via the objective lens. When identical images appear on both light valve arrays 3~8 and 31~, th~s may produce depixe-lization of the resulting image, which is desirable in certain applications, such as video displays. rAhen dif-ferent fields appear on the two light valve arrays, doubled image resolution in both mutually orthogonal directions may result.
By translating one or both of the light valve arrays 3~8 and 31~ dynamically, analogously to the embod-iment of Fig. 8, even greater increases in resolution can be achieved.
It is appreciated that light valve arrays 3~8 and 31~ may be monochromatic or polychromatic. Where the light valve arrays 3~8 or 31~ are monochromatic, a poly-chromatic projector may be realized by combining suitably filtered light passing through three parallel devices of the type illustrated in Fig. 11.
Reference is now made to Fig. 12, which is an illustration of a projector employing two light valve arrays in accordance with yet another embodiment of the present invention, which provides enhanced contrast. The embodiment of Fig. 12 may be identical to that of Fig. 11 and identical elements are shown by the same reference numerals, with the following exception:
Mirror 3~6 is replaced by a polarizing beam splitter 33~ which directs the s polarized component via light valve array 31~ as in the embodiment of Fig. 11. In accordance with a preferred embodiment of the invention, CA 02234643 l998-04-l4 - W O 97114076 PCT~L9C~
the polarizing beam splitter 33(3 is also effective to filter out a residual p component which impinges thereon together with the s component, and directs it in a direc-tion indicated by an arrow 332, thus removing it from the system and thus enhancing contrast.
Reference is now made to Fig. 13, which is an illustration of a color projector employing two light valve arrays in accordance with still another embodiment of the present invention, which provides enhanced con-trast. The embodiment oP Fig. 13 may be identic:~l to that of' Fig. 12 and identical elements are shown by the same reference numerals, with the following exception:
A color wheel 34~ or any other suitable device for sequentially transmitting the R, G and B spectral components of the beam is located intermediate the light source 3~)() and the polarizing beam splitter 302. This arrangement can be employed with particular utility when the light valve arrays 3~)8 and 31() are monochromatic, for providing a color projector.
Reference is now made to Fig. 14, which is an illustration of a color projector employing two light valve arrays in accordance with a further embodiment of the present invention, which provides enhanced contrast.
The embodiment of Fig. 14 may be identical to that of Fig. 12 and identical elements are shown by the same reference numerals, with the following exception:
In order to provide greatly enhanced light utilization at the light valves 3(~8 and 31(~), prism/lens combination arrays 35O and 352 are disposed upstream of respective light valve arrays 3O8 and 311~). The prism/lens ~ combination arrays 35~ and 352 may be of the type de-scribed and claimed in applicant/assignee's Published European Patent Application ~)631434.
As seen in Fig. 15, each component of an incom-ing collimated ray of light 354 is broken down by the prism/lens array 35~) into bands of different colors, CA 02234643 l998-04-l4 - - W 097/14076 - PCT~L9G/~ 5 each of which passes through a separate pixel in light valve 3~)8. This arrangement has substantial benefits in terms of light utilization efficiency as described in applicant/assignee's Published European Patent Applica-tion (~)6331434, the disclosure of which is hereby incorpo-rated by reference.
Reference is now made to Fig. 16, which is an illustration of a color projector employing two light valve arrays in accordance with still another ~mbodiment of the present invention. The embodiment of Fig. 16 may be identical to that of Fig. 11 and identical elements are shown by the same reference numerals, with the fol-lowing exception:
In order to provide greatly enhanced light utilization at the light valves 3(~)8 and 31(~), there are provided in front of mirror 3t~4 a pair of slightly tilted dichroic reflectors 360 and 362. Mirror 304 and dichroic reflectors 36(~ and 362 are together operative to provide a fan of the separate R, G and B components of light, each component being angularly separated from the other.
Similarly, there are provided in front of mirror 3(~)6 a pair of slightly tilted dichroic reflectors 364 and 366. Mirror 3t)6 and dichroic reflectors 364 and 366 are together operative to provide a fan of the sepa-rate R, G and B components of light, each component being angularly separated from the other.
The three mutually angularly separated compo-nents R, G and B impinge on respective lens arrays 368 and 37(~), which are disposed upstream of respective light valve arrays 308 and 310.
As seen in Fig. 17, each of the R, G and B
components of an incoming collimated ray of light 38(~) is focused by the lens array 368 through a separ~te pixel in light valve 3t~)8. This arrangement has substantial benefits in terms of light utilization efficiency as described in applicant/assignee's Published European CA 02234643 l998-04-l4 - W O 97/14076 PCT~L96,~~0CC
Patent Application 06331434, the disclosure of which is hereby incorporated by reference.
It is appreciated that the embodiments of Figs.
17 may be employed to provide stereo projection without the need for plural projectors. Reference is made, for example, to the embodiment of Fig. 11, wherein light valve arrays 3~8 and 31~ each represent information to be presented to a separate eye of a viewer, who wears conventional passive polarized eyeglasses. The lnformation to be presented to the left eye is provided, for example, by light valve array 3~8 with a vertical polarization and the information to be presented to the right eye is provided, for example, by light valve array 31~ with a horizontal polarization. The passive polarized eyeglasses in such a case would have vertical polarization in front of the left eye and horizontal polarization in front of the right eye.
It is appreciated that for simplicity and conciseness of description, not all of the standard components of a projector have been specifically de-scribed herein. These components include IR an~ UV fil-ters and fresnel lenses. It is to be understood that all conventional components of a projector are assumed to be - included in the projectors of the present invention even though they are not specifically mentioned herein.
It will be appreciated by persons s~illed in the art that the present invention is not limited by what has been particularly shown and described hereinabove.
Rather the scope of the present invention is defined only by the claims which follow:
Claims (27)
1. A projector comprising:
a non-polarized light source;
a polarizing beam-splitter receiving light from said non-polarized light source; and a selectably actuable polarization rotating light valve having light polarized in one sense from the polarizing beam-splitter impinging thereon from a first direction and having light polarized in an opposite sense from the polarizing beam-splitter impinging thereon from a second direction.
a non-polarized light source;
a polarizing beam-splitter receiving light from said non-polarized light source; and a selectably actuable polarization rotating light valve having light polarized in one sense from the polarizing beam-splitter impinging thereon from a first direction and having light polarized in an opposite sense from the polarizing beam-splitter impinging thereon from a second direction.
2. A projector according to claim 1 and wherein when the light valve is not actuated, the light polarized in both said one sense and said opposite sense passes therethrough without changes in polarization.
3. A projector according to claim 1 and wherein when the light valve is actuated, the light polarized in both said one sense and said opposite sense passes therethrough with changes in polarization to an extent determined by the actuation.
4. A projector according to claim 2 and wherein when the light valve is actuated, the light polarized in both said one sense and said opposite sense passes therethrough with changes in polarization to an extent determined by the actuation.
5. A projector according to claim 1 and wherein said light valve is operative when actuated to rotate the light passing therethrough in a range extending from 0 to 90 degrees.
6. A projector according to claim 1 and also comprising an objective lens arranged to receive light which has initially impinged on the beam splitter, passed through the light valve without polarization change and impinged on the beam splitter again.
7. A projector according to claim 1 and wherein the light valve is not actuated all of the light is directed to an objective lens.
8. A projector according to claim 6 and wherein the light valve is not actuated all of the light is directed to said objective lens.
9. A projector according to claim 1 and wherein when the light valve is actuated to cause a 90 degree rotation of the polarization, all of the light passing therethrough is directed back to the light source.
10. A projector according to claim 1 and wherein very small light losses and heat dissipation are encountered at the light valve, enabling relatively high brightness to be achieved using a relatively low power light source.
11. A projector according to claim 1 and wherein the light valve is a liquid crystal light valve from which polarization plates have been removed.
12. A projector according to claim 1 and wherein said light valve comprises a multiplicity of independently electrically actuable regions, corresponding to pixels.
13. A projector according to claim 1 and wherein said polarizing beam splitter comprises a pair of prisms which are cemented together with multiple dielectric layers therebetween.
14. A projector according to claim 1 and wherein said polarizing beam splitter is a crystallizing polarizing beam splitter.
15. A projector according to claim 1 and wherein said selectably polarization rotating light valve comprises:
a shutter assembly having a multiplicity of pixel light valves; and a color separator disposed on each side of the shutter assembly, intermediate the light source and the shutter assembly and spaced therefrom and providing a plurality of spatially separated differently colored light beams, wherein the plurality of spatially separated differently colored light beams are in predetermined registration with the multiplicity of pixel light valves.
a shutter assembly having a multiplicity of pixel light valves; and a color separator disposed on each side of the shutter assembly, intermediate the light source and the shutter assembly and spaced therefrom and providing a plurality of spatially separated differently colored light beams, wherein the plurality of spatially separated differently colored light beams are in predetermined registration with the multiplicity of pixel light valves.
16. A color projector comprising:
at least three monochromatic projector subassemblies, each including:
a non-polarized light source;
a polarizing beam-splitter receiving light from said non-polarized light source; and a selectably actuable polarization rotating light valve having light polarized in one sense from the polarizing beam-splitter impinging thereon from a first direction and having light polarized in an opposite sense from the polarizing beam-splitter impinging thereon from a second direction; and apparatus for combining the outputs of the at least three monochromatic subassemblies into a single image.
at least three monochromatic projector subassemblies, each including:
a non-polarized light source;
a polarizing beam-splitter receiving light from said non-polarized light source; and a selectably actuable polarization rotating light valve having light polarized in one sense from the polarizing beam-splitter impinging thereon from a first direction and having light polarized in an opposite sense from the polarizing beam-splitter impinging thereon from a second direction; and apparatus for combining the outputs of the at least three monochromatic subassemblies into a single image.
17. A projector comprising:
a non-polarized light source;
at least one polarizing beam-splitter receiving light from said non-polarized light source; and at least one selectably actuable polarization rotating light valve having light polarized in one sense from the polarizing beam-splitter impinging thereon from a first direction and having light polarized in an opposite sense from the polarizing beam-splitter impinging thereon from a second direction.
a non-polarized light source;
at least one polarizing beam-splitter receiving light from said non-polarized light source; and at least one selectably actuable polarization rotating light valve having light polarized in one sense from the polarizing beam-splitter impinging thereon from a first direction and having light polarized in an opposite sense from the polarizing beam-splitter impinging thereon from a second direction.
18. A projector comprising:
a non-polarized light source;
at least one polarizing beam-splitter receiving light from said non-polarized light source; and a pair of selectably actuable polarization rotating light valves having impinging thereon light from the polarizing beam-splitter which is polarized in a different sense.
a non-polarized light source;
at least one polarizing beam-splitter receiving light from said non-polarized light source; and a pair of selectably actuable polarization rotating light valves having impinging thereon light from the polarizing beam-splitter which is polarized in a different sense.
19. A projector according to claim 18 and wherein the pair of selectably actuable polarization rotating light valves operate in a reflective mode.
20. A projector according to claim 18 and wherein said at least one polarizing beam-splitter comprises a pair of polarizing beam splitters and pair of selectably actuable polarization rotating light valves operate in a transmissive mode.
21. A projector according to claim 21 and being operative to provide selectably normally white or normally black modes of operation.
22. A projector according to claim 20 and also comprising an additional beam splitter operative to filter out unwanted residual polarized light thereby enhancing contrast.
23. A projector according to claim 22 and wherein said light valves are monochromatic and also including a device for sequentially transmitting the R, G and B
spectral components of the beam, onto at least one polarizing beam splitter.
spectral components of the beam, onto at least one polarizing beam splitter.
24. A projector according to claim 20 and also comprising prism/lens combination arrays disposed upstream of said light valves.
25. A projector according to claim 20 and also comprising lens combination arrays disposed upstream of said light valves.
26. A projector according to claim 20 and also comprising apparatus for providing depixilization.
27. A projector according to claim 20 and also comprising apparatus for providing interlaced images with enhanced resolution.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US08/543,219 US5833338A (en) | 1995-05-19 | 1995-10-13 | Projector |
| US08/543,219 | 1995-10-13 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2234643A1 true CA2234643A1 (en) | 1997-04-17 |
Family
ID=24167089
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002234643A Abandoned CA2234643A1 (en) | 1995-10-13 | 1996-07-24 | Projector |
Country Status (6)
| Country | Link |
|---|---|
| EP (1) | EP0880725A4 (en) |
| JP (1) | JPH11513504A (en) |
| CN (1) | CN1214127A (en) |
| AU (1) | AU6529996A (en) |
| CA (1) | CA2234643A1 (en) |
| WO (1) | WO1997014076A1 (en) |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR100792603B1 (en) * | 1998-06-05 | 2008-01-09 | 세이코 엡슨 가부시키가이샤 | Light source and display device |
| US6317169B1 (en) * | 1999-04-28 | 2001-11-13 | Intel Corporation | Mechanically oscillated projection display |
| JP4461021B2 (en) * | 2002-12-04 | 2010-05-12 | トムソン ライセンシング | High contrast stereo projection system |
| EP2067066B1 (en) * | 2006-09-29 | 2014-11-05 | RealD Inc. | Polarization conversion systems for stereoscopic projection |
| CN107861310A (en) * | 2017-11-27 | 2018-03-30 | 深圳市华星光电技术有限公司 | A kind of double-lens laser projection display equipment |
| CN107885022A (en) * | 2017-12-28 | 2018-04-06 | 深圳市华星光电技术有限公司 | Double-lens laser projector display device and its application method |
| DE102018110117A1 (en) | 2018-04-26 | 2019-10-31 | Carl Zeiss Microscopy Gmbh | Optical arrangement and method for light beam shaping for a light microscope |
Family Cites Families (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5235444A (en) * | 1988-08-26 | 1993-08-10 | U.S. Philips Corporation | Image projection arrangement |
| JPH02153336A (en) * | 1988-12-05 | 1990-06-13 | Sharp Corp | Projection type liquid crystal display device |
| US4911547A (en) * | 1989-06-07 | 1990-03-27 | Hughes Aircraft Company | Compact optical system for a single light valve projector using two axes of polarization |
| KR930003307B1 (en) * | 1989-12-14 | 1993-04-24 | 주식회사 금성사 | Three dimensional projector |
| FR2665773B1 (en) * | 1990-08-10 | 1993-08-20 | Thomson Csf | IMAGE PROJECTION DEVICE USING TWO ORTHOGONAL LIGHT POLARIZATION COMPONENTS. |
| JP2575558Y2 (en) * | 1990-12-26 | 1998-07-02 | エルジー電子株式会社 | Optical system structure of liquid crystal projection display |
| JPH05257110A (en) * | 1992-03-13 | 1993-10-08 | Sharp Corp | Projection type liquid crystal display device |
| US5428469A (en) * | 1993-11-16 | 1995-06-27 | Minnesota Mining And Manufacturing Company | Liquid crystal display projection systems employing polarizing beam splitters and passing light through display cell from both directions |
-
1996
- 1996-07-24 WO PCT/IL1996/000065 patent/WO1997014076A1/en not_active Application Discontinuation
- 1996-07-24 AU AU65299/96A patent/AU6529996A/en not_active Abandoned
- 1996-07-24 CA CA002234643A patent/CA2234643A1/en not_active Abandoned
- 1996-07-24 CN CN96198374A patent/CN1214127A/en active Pending
- 1996-07-24 EP EP96925058A patent/EP0880725A4/en not_active Withdrawn
- 1996-07-24 JP JP9514888A patent/JPH11513504A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| CN1214127A (en) | 1999-04-14 |
| EP0880725A4 (en) | 2000-01-05 |
| EP0880725A1 (en) | 1998-12-02 |
| WO1997014076A1 (en) | 1997-04-17 |
| JPH11513504A (en) | 1999-11-16 |
| AU6529996A (en) | 1997-04-30 |
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