CA2264887A1 - Method and apparatus for presenting a visual display to an audience - Google Patents

Abstract

Immersive wide field of view displays are disclosed, for example, in the context of a virtual reality environment. At least two different sets of images are presented for a corresponding number of groups of viewers. In one aspect of the invention, each group has its own projection screen and projector and the viewers and screens are located in close proximity to one another for allowing interaction between the groups, but with the viewing screen for each group outside the field of view of the viewers of the other group. In another aspect of the invention, two different sets of stereoscopic images are projected onto the same screen that is viewed by two groups of viewers. Separation of the respective sets of images and of the left and right eye images within each set are achieved using either an alternate eye technique or a polarizer image separation technique. Time-multiplexing of images coupled with corresponding shuttering of viewers' eyes is also disclosed for achieving presentation of separate images to different groups of viewers.

Description

CA 02264887 1999-03-03W0 98/11737 PCT/CA97/00653_ 1 -Title: METHOD AND APPARATUS FORPRESENTING A VISUAL DISPLAY TO AN AUDIENCEFIELD OF THE INVENTIONThis invention relates to a method of presenting a visual5 display to an audience. The invention has been devised primarily (but not1015202530exclusively) in connection with so-called ”immersive” wide field—of-viewdisplays. In this context, the term ”immersive” means that the viewerexperiences a high sense of realism or ”immersion” in the display, forexample, as in a virtual reality environment.BACKGROUND OF THE INVENTIONA number of approaches currently are used to provide anexciting and immersive visual environment for entertainment purposes.One such approach makes use of large film format motion pictureequipment such as that supplied by Imax Corporation to provide highresolution images which completely fill a viewer's field of view. Visualcues which may remind viewers that they are watching a motion pictureare effectively removed, thereby creating a sense of immersion orinvolvement in the action being depicted on the screen.The sense of immersion can be further enhanced byprojecting stereoscopic large format motion pictures onto a wide field ofview screen. The large viewing angles associated with such a screengreatly increases the stereoscopic viewing space in which 3-D objects can bepositioned and viewed. Several methods of presenting stereoscopicimages currently are used; the most common are polarization andelectronic ”alternate eye” separation of images. In polarizationstereoscopic projection, linear polarizer filters are placed respectively infront of left eye and right eye projectors with their polarizing axes at 90degrees to each other. Viewers wear eyeglasses with polarizing filtersarranged in the same orientation as the filters on the projectors. The left-eye and right—eye images appear on the screen at the same time, but onlythe left eye polarized light is transmitted through the left eye lens of theW0 98/117371015202530CA 02264887 1999-03-03PCT/CA97/00653- 2 -eyeglasses and only the right eye polarized light is transmitted through theright eye lens.In electronic alternate eye stereoscopic projection, left-eye andright—eye images are presented alternately so that there is only one eyeimage on the screen at any moment in time. Viewers wear glasses whichalternately block the View of one eye so that only the correct images willbe seen by each eye. The glasses typically have electro-optic liquid crystalshutters and are powered by batteries. 3-D motion picture systems of thistype are disclosed in U.S. Patents Nos. 4,957,361 (Shaw), 4,966,454(Toporkiewicz), and 5,002,387 (Baljet et al.). A method of improving theperformance of polarizer stereoscopic 3-D is presented in U.S. Pat. No.5,402,191 (Dean et al.). An improved so-called ”hybrid” shutter is disclosedin Canadian Patent Application No. 2,146,811 filed April 11, 1995. All ofthese references have been assigned to Imax Corporation. Theirdisclosures are hereby incorporated by reference.The sense of "realism or immersion of a display can beenhanced by providing for interaction between audience members and thedisplay system so that the audience members have some degree of controlover what they are seeing. Usually this kind of user control is restricted tosingle viewer displays only, such as those known as head mounteddisplays (HMD's).the display. However, because of technology limitations, in practice, theA viewer wearing a HMD is completely immersed inviewer can only see a very low resolution image. Another disadvantageof HMD's is that the viewer is completely isolated visually from otherparticipants, so it is difficult to devise an engaging group experience.There have been attempts to provide an interactive,immersive experience. For example, a system has been marketed byIwerks under the trade mark ”VIRTUAL ADVENTURES” in which asmall group of people sit in the same vehicle simulator. In such a system,a front or main display is usually presented as a vehicle window orviewport. This restricts the visual field of View provided to theparticipants. The narrow field of View translates to a limited stereoscopicWO 98/117371015202530CA 02264887 1999-03-03PCT/CA97/00653- 3 _Anotherdisadvantage of such a system is that the narrow field of view restricts theor 3-D space and the sense of immersion is compromised.placement of audience members within the vehicle simulator. As a result,some audience members are seated in good viewing locations while othersare located in poorer viewing locations. The result is a lack of experienceequality for all members of the audience which can lead to disappointmentfor some participants.DESCRIPTION OF RELATED ARTThere are several examples of multiple point of view displaysin the prior art:U.S. Patent No. 5,260,729 to Ullah et al. discloses an apparatusand method for displaying non—interfering color images to two or moreviewers. A first set of images is generated from a first set of colorwavelengths and a second set from a second set of color wavelengths. Thetwo sets of wavelengths are spectrally multiplexed to include first andsecond red, green and blue wavelengths. A first viewer views the imagesthrough a filter which transmits the first set of wavelengths, but rejects thesecond set of wavelengths. A second viewer views the images from a filterwhich transmits the second set of wavelengths but rejects the first set ofwavelengths.U.S. Patent No. 4,879,603 to Berman discloses a multipleimage single display apparatus and method. A monochromatic displaysource provides first and second sets of images which alternate rapidly.The images pass through an active polarization assembly which polarizesall of the images of the first set to a left handed circular polarization and allof the images of the second set to right handed circular polarization.A first viewer wears passive glasses which reflects right-handed polarized light and a second viewer wears passive glasses whichreflects left-handed polarized light.U.S. Patent No. 4,657,512 to Mecklenborg discloses a displaysystem for a vehicle simulator which allows two individuals to see imagescorrect for their point of View in front of a curved projection screen. TwoU]1015202530oCA 02264887 1999-03-03-00 0 0 O I O0 0I 0 I00 I0 O 0 D IO O O I0000 no soprojectors are used; a left-handed circular polarizer filter is placed in frontof one and a right-handed circular polarizer is placed in front of the other.Two separate Windshields are provided, each of which has a circularpolarizer filter placed in front so that the images from a first one of theprojectors are transmitted by a first windshield and not a secondwindshield, and the images from the second projector are transmitted bythe second windshield and not the first windshield.SUMMARY OF THE INVENTIONThe present invention is based on the realization that there isa need for a visual display system which allows multiple points of viewand social interaction between groups of viewers (audience groups).Preferably, the system should be both visually immersive and provide foran engaging, interactive group experience.The invention provides a method of presenting a visualdisplay to an audience, comprising the steps of: providing two points ofview for two groups of viewers; projecting onto a viewing screen visiblefrom both points of view, respective sets of stereoscopic images, one foreach group of viewers, each set comprising a series of right-eye images anda corresponding series of left-eye images; separating the respective sets ofimages so that each group of viewers sees only the images intended forthat group; and, within each set of images, presenting the left-eye imagesof that set only to the left eye of each viewer in the respective group andpresenting the right-eye images only to the right eye of each viewer in thatgroup;the viewers in each group see stereoscopic images but only those that arewhereby both groups of viewers watch the same screen andintended for the particular group and not the images that are intended forthe other group.The expression "point of view" as used in the presentdisclosure and claims in relation to a group of viewers (audience group)refers to the images that are presented to the viewers in the group, not tothe physical location or attitude of the viewers. References to two groupsof viewers having different points of view means that each viewer in anyAMENDED SHEETU]1015202530CA 02264887 1999-03-03-5-one group sees the same images and that those images are different fromthe images seen by the viewers in the other group. For example, the twopoints of view may be represented by images from a common scene orenvironment, but seen from different perspectives or vantage points.Preferably, a wide-field of View stereoscopic display is usedand provides multiple unique points of view simultaneously to multiplegroups of participants in such a manner that each group can only see theset of images intended for them and not any of the other sets of imagesassociated with other groups. The unique and exclusive point-of—view ofeach group allows for independent interaction. The display can be ashared computer generated virtual environment.Electronic display projectors preferably are used. It should beunderstood that, wherever this term is used in the disclosure and claims,it is intended to be interpreted broadly as including a wide range ofelectronic projection systems having different resolution and imagequality characteristics. Included within this term are graphics projectorstypically having resolutions up to 2000 x 2000 pixels, data projectors for usewith personal computers having resolutions up to 1024 x 768 pixels, highdefinition television projectors (HDTV) providing up to 1125 lines with anaspect ratio of 16,9, and video projectors suitable for suitable NTSCresolution (typically 380 - 480 lines). Reference may be made to ”ElectronicDisplays: Technology, Design and Applications” Gerry C. Whitaker,McGraw-Hill, New York, 1994 for further discussion of display projectors.In a preferred embodiment, first and second electronic displayprojectors and one projection screen are provided. The first projector hasa first linear polarizer filter in front of its lens, with the polarization axis inone direction. The second projector has a second linear polarizing filter infront of it's lens oriented at 90 degrees with respect to the axis of the firstpolarizing filter. Viewers in a first audience group wear electronicalternate eye glasses which have linear polarizers on the front surface ofthe lenses oriented to transmit images from the first projector but to blockimages from the second projector. Similarly, viewers in a second audienceAMENDED SHEET102025_CA 02264887 1999-03-03-6-group wear electronic alternate eye glasses which have linear polarizers onthe front surfaces of their lenses which are oriented to transmit imagesfrom the second projector and block images originating from the firstprojector. Each projector alternately projects left and right eye images insynchronism with the opening and closing of the liquid crystal shutters inthe electronic alternate eye glasses.In an alternative embodiment, the left and right shutters ofthe glasses are opened and closed simultaneously and each group's glassesbeing driven out of phase so that while one groups‘ shutters are bothopen, the other audience groups’ shutters are both closed. In such aconfiguration, a first projector projects the left eye images for a firstaudience group and the right eye images for a second audience group, anda second projector projects the right eye images for the first audience groupand the left eye images for the second audience group.Either embodiment allows each audience group to see fullstereoscopic wide field-of~view unique images while simultaneouslylooking at the same screen at the same time. The two audience groupscan be located in close physical proximity thereby allowing stimulatingvisual and verbal interaction between the two groups. In addition, becausethe two groups are located closely together, each participant will haveroughly equal fields of view of the screen resulting in a perception ofexperience equality among all participants.An apparatus corresponding to each method aspect of theinvention is also provided.BRIEF DESCRIPTION OF DRAWINGSIn order that the invention may be more clearly understood,reference will now be made to the accompanying drawings whichillustrate preferred embodiments of the various aspects of the invention,and in which:Figs. 1a) and b) are respectively diagrammatic plan and sideelevational Views illustrating an arrangement of projectors, screens andaudience groups in accordance with a first aspect of the invention;AMENDED SHEETCA 02264887 1999-03-03-7-Figs. 2 is a View similar to Fig. la) illustrating a furtherembodiment of this aspect of the invention;Figs. 2a and 2b illustrate images that may appear on thescreens in the embodiments of Figs. 1a) and b) and Fig. 2;Fig. 3 is a View similar to Fig. la) illustrating a second aspectof the invention;Fig. 4 comprises a block diagram denoted a), which illustratesa system for projecting two independent sets of stereoscopic images onto asingle projection screen as shown in Fig. 3, and diagrammatic illustrationsW0 98/117371015202530CA 02264887 1999-03-03PCT/CA97l00653- 3 _denoted b) and c), which show the corresponding polarization of electronicglasses worn by two groups of viewers;Fig. 5 comprises three timing diagrams denoted a), b), and c)illustrating the timing of the alternate images for one of the projectorsshown in Fig. 4;Fig. 6 is a view similar to Fig. 4 and contains the sameillustrations a), b) and c) for an alternative embodiment of this aspect ofthe invention;Fig. 7 is a View similar to Fig. 5 but comprising six timingdiagrams denoted respectively a), b), c), d), e), and f) for the embodiment ofFig. 6;Fig. 8 illustrates similar timing diagrams denoted a), b), c),and cl) for a further embodiment of the invention in which images arepresented to four separate audience groups; and,Fig. 9 is a further View illustrating timing diagrams denoteda), b), c), d), and e) for a still further embodiment of the invention inwhich separate points of View are presented to four groups of viewersusing a single projector. _DESCRIPTION OF PREFERRED EMBODIMENTSFigs. 1 and 2 illustrate the first aspect of the inventionreferred to previously, in which there is provided, for each of two groupsof viewers (audience groups), a projection screen, a projector for projectinga set of images onto that screen and a point of view for the group ofviewers in front of the screen. The respective points of View and theviewing screens are located so that the groups of viewers are in closeproximity to one another and the viewing screen for each group ofviewers is located outside the field of View of the Viewers of the othergroup.Referring first to Figs. 1 a) and lb), a first electronic projector20 projects images onto a projection screen 22. Seated in front of screen 22is an audience group 24 consisting of two people. Similarly, a secondelectronic projector 26 projects images on projection screen 28 located inW0 98/117371015202530CA 02264887 1999-03-03PCT/CA97/00653_ 9 -front of a second audience group 30. In the drawings, the points of viewreferred to previously are represented by the diagrammatic illustrations ofpeople.The projectors 20 and 26 preferably are high resolutionOne suchprojector is available under the trade mark ELECTROHOME MARQUIS3000.preferably are generated by a simulation computer thereby allowing real-projectors, capable of at least 1000 lines of vertical resolution.Though not essential to the invention, the projected imagestime interaction between the audience groups and the images they see.Audience members are then provided with an input device such as ajoystick or spaceball (not shown) with which they can enter commands,directions or selections to the simulation computer to affect a change inthe simulated environment or their current point of View of theenvironment. These features may be provided in accordance with knowntechniques and accordingly are not described in detail here.Audience groups 24 and 30 are arranged back to back so thatthey are still close together, within normal audible speech range of eachother, and also so that only their own projection screen is visible.Fig. 2 shows a similar embodiment but with the screens andaudience groups located at right angles to each other. Primed referencenumerals are used to denote elements that correspond with elementsshown in Figs. 1a) and b). Of course, relative angular orientations arepossible other than right-angular.In either embodiment, the projectors may (but need notnecessarily) display full colour stereoscopic images to each group by thealternate eye method of stereoscopic separation. In such a case, audiencemembers would require electronic alternate eye glasses to properly receivethe stereoscopic images, for example as taught in the referencesincorporated herein (supra). Since the images are exclusively presented tothe respective audience groups, each group can have a completelyindependent view from that of the other group enabling separate andindependent interaction with the simulation. The proximity of theW0 98/117371015202530CA 02264887 1999-03-03PCT/CA97/00653_ 10 _audience groups allows for friendly social interaction between the twogroups as the entertainment experience unfolds, which can involve eithercooperation or competition between the two groups.The images viewed by the respective groups of viewers maybe related for enhancing interaction between the groups. Figs. 2a and 2billustrate an example of such related images as seen by two viewer groups.In a non-interactive experience, Group 1 viewers could beseeing a narrative from one point of view, say, the police. In the exampleillustrated, the viewers would see an overhead helicopter View of afugitive’s getaway car. Group 2 would see the narrative from the point ofview of the fugitive in the getaway car.In an interactive experience, team members would havecontrol over the vehicles depicted on the screens through computer inputdevices connected to computers running a real-time simulation.Fig. 3 illustrates a second aspect of the invention, in whichdouble primed reference ‘numerals have been used to denote elementsthat correspond to elements shown in Figs. 1a) and b). Two electronicprojectors 20" and 26" project images onto a single projection screen. Twoaudience groups 24" and 30" are located beside each other in front of screen32. Each group sees a unique set of images. Although the audiencemembers are shown in two side-by-side groups, they could in fact belocated in any physical arrangement including an alternating arrangementsuch as team 1 - team 2 - team 1 - team 2 because the method of imageseparation is independent of audience location within the viewing zone.Referring to Fig. 4, a control computer 34 contains a databaseof all objects and events which define a simulated world or environment.The control computer regularly sends current information of thesimulated environment to four graphics computers, 36, 38, 40 and 42, eachof which render images in real time for each of four points of view.Computer 36 for instance renders images intended for the left eyes of afirst audience group (group 24" in Fig. 3), while computer 38 rendersimages for the right eye of the same group. Similarly, computers 40 andW0 98/117371015202530CA 02264887 1999-03-03PCT/CA97/00653_ 11 -42 render images for the left and right eyes of a second audience group (30”in Fig. 3). It has been found that high end personal computers such asthose that have Pentium processors are sufficient for the purposes ofmaintaining and rendering the simulated environment. It has beenfound necessary to enhance the rendering computers with 3D graphicsaccelerators such as the ”3Deamon” supplied by Omnicomp.The data generated by computers 36 and 38 are transmitted toprojector 20" (see also Fig. 3). A linear polarizing filter 44 is arranged infront of the lens of projector 20" with its polarizer axis horizontal(indicated by arrow ”H"). Computers 40 and 42, likewise transmit data toelectronic projector 22" which has a linear polarizer filter 46 arranged sothat its polarization axis is vertical (arrow ”V”). Viewers in the firstaudience group 24" members wear electronic liquid crystal shutter glasses48, which have both of their outer linear polarizers oriented so that theirpolarizer axes are horizontal (”H”) and thereby parallel to the axis of thepolarizer 44 in front of projector 20". Likewise the viewers in audiencegroup 30" wear electronic glasses 50 which have both of their outerpolarizers oriented to be vertical and thereby parallel to the axis of thepolarizer 46 in front of projector 22".The orthogonal linear polarizers in front of the lenses of theprojectors effectively create two separate points of view when used withthe corresponding glasses 48 and 50. Projectors 20" and 22" are driven toalternately project left and right eye images, and the images are alternatelytransmitted and blocked by the liquid crystal shutters of glasses 48 and 50,thereby allowing the simultaneous presentation of two separatestereoscopic points-of-view.Suitable techniques for constructing and driving theshuttered glasses 48 and 50 are well-known to people skilled in the art andare discussed in some of the references incorporated herein. Liquid crystalshutters used in glasses for 3-D viewing each incorporate two linearpolarizers on either side of a liquid crystal cell. The two polarizers areoriented with their axes orthogonal to one another and the liquid crystalWO 98/117371015202530CA 02264887 1999-03-03PCT/CA97/00653_ 12 _material acts as a variable polarizer influenced by an electric field. Thepolarizers may be appropriately oriented in constructing the glasses so thatthe outer polarizer is positioned to function in accordance with themethod described herein.Fig. 5 illustrates the timing of the alternating images forprojector 20". In Fig. 5a) one complete image ”frame” is depicted by theline denoted 52, representing the time during which that frame isdisplayed. The frame consists of a left eye image L1, followed by a right eyeimage R1, followed by the same left eye image, followed by the same righteye image. The frame rate is typically 30 Hz in normal video applications,but because of the limitations of the graphics processing hardware theframe rate of the disclosed invention is typically 1520 Hz. To avoidobjectionable flicker it is necessary to present each image twice during oneframe so that the flicker rate is elevated to 30-40 Hz. The duration of oneflicker or field is depicted by 54 and is typically 1/60 to 1/80 Hz.Fig. 5b) illustrates the timing of the left eye shutter for theviewers in the first audience group (24”). The transmission of the shuttervaries from 0 to 100% and is timed so that it is fully open when projector20" is projecting a left eye image and fully closed when a right eye image isprojected. Similarly, Fig. 5c) shows the timing for the right eye shutter.The arrows at the left in Figs. 5a), b) and c) illustrate the orientation of thelinear polarizer 44 associated with projector 20 and of each shutter in theglasses of the audience group. The timing diagrams for the left and righteye shutters for the members of the second audience group will be thesame.To summarize, in the embodiment of Fig. 4, the sets ofstereoscopic images that are intended for the first group of viewers areprojected exclusively by the first projector, 20", and the left and right eyeimages within that set are separated from one another using the ”alternateeye” technique. The same applies to the sets of images for the viewers inthe second group. The viewers in the respective groups see only thoseimages that are intended for that group because of polarizers 44 and 46 thatW0 98/117371015202530CA 02264887 1999-03-03PCT/CA97/00653_ 13 _are associated with the respective projectors and the correspondinglypolarized glasses that are worn by the Viewer groups.In other words, the polarizers provide means for separatingthe respective sets of stereoscopic images and the "alternate eye" techniquecomprises means for presenting, within each set of images, the left eyeimages only to the left eye of the viewer, and the right eye images only tothe right eye of a viewer in the relevant group.Fig. 6 illustrates an alternative embodiment of the inventionin which the techniques for separating the sets of images intended for therespective groups and the left eye and right eye images within those sets ofimages are reversed. In other words, in the embodiment of Fig. 6, thealternate eye technique is used to separate the respective sets of images forthe two groups of Viewers, and the polarizer technique is used to separatethe left and right eye images within each set. Thus, the elements shown inFig. 6 are the same as the elements shown in Fig. 5 (and are similarlydesignated). The only difference is that, in each pair of eyeglasses (48 and50) the polarizer in the left eye lens is horizontally polarized and thepolarizer in the right eye lens is vertically polarized, as indicated by therespective arrows denoted H and V. The computers 36, 38, 40 and 42 alsogenerate the images differently. The computers 36 and 38 generaterespectively the left eye images and the right eye images for the first groupof viewers but the left eye images are projected by the first projector 20",whereas the right eye images are projected by the second projector 22".Similarly, the left eye images for the second group of viewers, generated bycomputer 40, are projected by the second projector 22", whereas the righteye images for that same group of viewers are projected by the firstprojector 20".Fig. 7 illustrates the timing for the embodiment of Fig. 6. InFig. 7a) the output of the first projector 20" alternates between a left eyeimage for the first audience group and a right eye image for a secondaudience group. Similarly, Fig. 7b) shows that the output of the secondprojector 22" alternates between right eye images for the first audienceW0 98/117371015202530CA 02264887 1999-03-03PCT/CA97/00653_ 14 _group and left eye images for the second audience group. The arrows Hand V at the left of the timing diagrams represents the orientation of thepolarizers in front of the lenses of the first and second projectors.Referring to Fig. 7a), the designation L11 denotes the left eyeimage —- audience group 1 - frame 1 and R21 indicates the right eye image --audience group 2 - frame 1. In other words, the first integer is a letterdesignating left eye or right eye image, the second integer is a numberindicating the first or second audience group and the subscript is a numberindicating the particular frame in the sequence being displayed.Figs. 7c) and d) illustrate the timing of the opening andclosing of the liquid crystal shutters in the glasses worn by the first groupof viewers (24”). The timing is arranged so that the left and right eyeshutters are opened and closed together in synchronism. Figs. 7e) and f)illustrate the timing of the shutters for the glasses worn by members of thesecond viewer group (30”).As can be seenmin the diagrams, the respective sets of imagesare ”time multiplexed” and are never projected onto the screen at thesame time. The separation of left and right eye images within each set isaccomplished by the orientation of the polarizers on the glasses and infront of each projector. An advantage of the Fig. 6 embodiment is that theamount of ghosting or cross-talk between the two audience groups imagesis noticeably less than is the case when polarizers are used for imageseparation. This is particularly useful since the ghosting between theaudience groups views is often more noticeable and objectionable than isthe case between left and right eye image ghosting.In summary, using the embodiment of Fig. 4 or theembodiment of Fig. 6, respective sets of stereoscopic images can beprojected onto the same viewing screen for two different groups ofviewers. The viewers in each group do not see the images for the othergroup. The system may be passive or interactive. For example, viewerscould be provided with input devices such as a joystick or spaceball asdiscussed previously in connection with Figs. 1a), 1b.) and 2 to effect aW0 98/1 17371015202530CA 02264887 1999-03-03PCT/CA97I00653_ 15 _change in the simulated environment or their current point of view of theenvironment. In Figs. 4a) and 6a), input devices for the viewers of the twogroups of viewers are represented at 11 and 12 respectively. The respectivegroups of viewers could, for example, be given the sensation of drivingdifferent cars on the same road or on a racetrack, or playing hide-and-seekwithin a maze. While neither group of viewers would see the viewpointof the other group, an indication of that viewpoint, for example, theposition of the other ”person” (for example the other driver in a race carsituation or the other person in a maze) may be provided in the form of agraphical icon or ”avatar” such as is typically used to represent the ”otherperson” in virtual reality environments.Fig. 8 shows timing diagrams presenting images to fourseparate audience groups in accordance with a further aspect of theinvention. The large numbers 1 to 4 represent the images for the fourgroups and the subscripts represent the frame sequence (each frame isprojected twice). Fig. 8a)lshows that the images for groups 1 and 2 aretime-multiplexed and projected by a first projector having a horizontallyaligned linear polarizer in front of its lens. Similarly and as shown in Fig.8b), a second projector projects time—multiplexed images for groups 3 and 4and has a vertically oriented linear polarizer in front of its lens. Figs. 8c)and d) illustrate the timing of the liquid crystal glasses that are Worn bygroups 1 and 3 followed by groups 2 and 4 respectively.Both lenses in the glasses worn by the viewers of groups 1and 2 are horizontally polarized so that the viewers in those groups cannotsee the images projected for the viewers of groups 3 and 4. Conversely,both lenses in the glasses worn by the viewers of groups 3 and 4 arevertically polarized. Both eyes of the viewers of group 1 are blocked (i.e.the glasses worn by members of that croup are opaque) when the imagesfor group 2 viewers are being projected, and vice versa. Similarly, botheyes of the viewers of group 3 are blocked when the images for group 4 arebeing projected, and vice versa. In other words, the images for groups 1and 2 are separated from one another by time multiplexing and from theW0 98/1 1 7371015202530CA 02264887 1999-03-03PCTICA97/00653-16-images of groups 3 and 4 by means of the polarizers. Similarly, as betweengroups 3 and 4, the images are separated by time multiplexing, and thoseimages are separated from the images of groups 1 and 2 by the polarizers.Fig. 9 illustrates another embodiment of the invention inwhich different two-dimensional images are presented to four groups ofviewers using a single projector. As shown in Fig. 9a) an electronicprojector projects four time-multiplexed fields or images in the same timethat is normally used to present two fields or images. Each image isprojected twice. The projector must necessarily have rapid turn on and offof the projected images to allow such multiplexing; projectors capable ofthis are those based on a digital mirror device (DMD) imaging chip such asthose manufactured by Texas Instruments. Figs. 9b) - e) illustrate thetiming of the liquid crystal shutter glasses for the four audience groups. Inother words, in the embodiment of Fig. 9, the images for the four groupsare projected from a single projector in time-multiplexed fashion and theglasses for the four groupsof viewers are triggered in synchronism, so thatthe eyes of a particular viewer are unobscured only during the time forwhich the image intended for that group is on the screen. A secondprojector and orthogonal linear polarizer filters can be added to add eitheran additional four audience groups or to add stereoscopic images for thefour initial groups.While the present invention has been described herein withreference to particular embodiment, it is understood that the invention isnot limited thereto. The teachings of this invention may be used by onehaving ordinary skill in the art to make modifications thereof. Forexample, although linear polarizers have been described as an element ofthe invention, circular polarizers could be used instead. Also, althoughthe invention has been described in the context of a computer driveninteractive experience the invention could be used with non-interactivepassive displays originating from film, video, laser disk etc.Also, while the claims refer specifically to two groups ofviewers (audience groups), it is of course to be understood that, withinCA 02264887 1999-03-03W0 98/ 11737 PCT/CA97/00653-17-technical limitations, multiples of two groups can be accommodated, asexemplified in the disclosure above.

Claims (17)

WE CLAIM:

1. A method of presenting a visual display comprising the steps of:
providing an audience comprising two groups of viewers having respective points of view;
providing a viewing screen visible from both of said points of view;
projecting onto said screen, respective sets of stereoscopic images, one for each group of viewers, each set comprising a series of right-eye images and a corresponding series of left-eye images;
separating the respective sets of images so that each group of viewers sees only the images intended for that group; and, within each set of images, presenting the left-eye images of that set only to the left eye of each viewer in the respective group and presenting the right-eye images only to the right eye of each viewer in that group;
whereby both groups of viewers watch the same screen and the viewers in each group see stereoscopic images but only those that are intended for the particular group and not the images that are intended for the other group.

2. A method as claimed in claim 1, wherein the respective sets of images are separated by optically coding for each group the images that are projected onto the screen, and providing each viewer with corresponding optical decoding means selected so that each viewer in a particular group sees only those images that are coded for that particular group, and wherein left-eye and right-eye images within each set of images are projected alternately and each viewer is provided with optical shutter means that alternately block the eyes of the viewer in synchronism with the projected images so that the viewer's left eye receives only left- eye images and the viewer's right eye receives only right-eye images.

3. A method as claimed in claim 1, wherein the respective sets of images are separated by alternately projecting images from the respective sets and providing each viewer with optical shutter means that block the eyes of the viewer in synchronism with the projection of the sets of images so that a viewer in each group sees only the images intended for that group, and wherein the left-eye and right-eye images within each set of images are separated by optically coding the images and providing each viewer with corresponding optical decoding means selected so that the right eye of each viewer receives only a correspondingly coded right-eye images and the left eye of each viewer receives only correspondingly coded left-eye images.

4. A method as claimed in claim 3, wherein said step of projecting respective sets of stereoscopic images is performed by projecting the right-eye images from first projection means, and projecting the left-eye images for both sets of images from second projection means, wherein the respective projection means are provided with mutually extinguishing polarizing filters, and wherein the optical decoding means provided to the viewers comprise correspondingly polarized filters arranged so that the right eye of each viewer can receive right-eye images from the first projection means only and the left eye of each viewer can receive left-eye images from the second projection means only.

5. A method as claimed in claim 2, wherein said step of projecting the images is performed by projecting each set of images using separate projection means, wherein said step of optically coding the projected images is performed by providing said projection means with mutually extinguishing filters, and wherein said optical decoding means comprises correspondingly polarized filters worn by the viewers so that each viewer can see images projected by only one of said projection means.

6. A method as claimed in claim 1, wherein the respective sets of images are separated so that each group of viewers sees only the images intended for that group, by projecting the images from each set at intervals separated in time, and alternately blocking and exposing the eyes of the viewer in synchronism with the projection of the images, so that each viewer sees only the images intended for his or her group.

7. A method as claimed in claim 6, for presenting visual display to four groups of viewers identified as group 1, group 2, group 3, and group 4, wherein the images are displayed in repeating sequences comprising an image intended for group 1, an image intended for group 2, an image intended for group 3 and an image intended for group 4, and wherein, when an image intended for a viewer of a particular group is being projected, the eyes of the viewers of the other groups are blocked by said electro-optical shutter means.

8. A method as claimed in claim 7, wherein the images in the respective said sequences are alternating left-eye and right-eye images, and wherein the electro-optical shutter means are timed to alternately block the eyes of each viewer during alternate said sequences for each set of images in synchronism with the projected images so that the left eye of each viewer receives only left-eye images and the right eye of each viewer receives only right-eye images.

9. An apparatus for presenting a visual display to an audience, comprising two groups of viewers having respective points of view, the apparatus comprising:
a viewing screen visible from both of said points of view;
means for projecting onto said screen, respective sets of stereoscopic images, one for each group of viewers, each set comprising a series of right-eye images and a corresponding series of left-eye images;
means for separating the respective sets of images so that each group of viewers sees only the images intended for that group; and, means for presenting, within each set of images, the left eye images of that set only to the left eye of each viewer in the respective group and presenting the right eye images only to the right eye of each viewer in that group;
whereby both groups of viewers watch the same screen and the viewers in each group see stereoscopic images but only those that are intended for the particular group and not the images that are intended for the other group.

10. Apparatus as claimed in claim 9, wherein the said means for separating the respective sets of images comprise means for optically coding for each group the images that are projected onto the screen and optical decoding means for each viewer selected so that each viewer in a particular group sees only those images that are coded for that particular group, and wherein the said means for presenting left and right eye images within each set of images comprises means for alternately projecting those images and optical shutter means for each viewer adapted to alternately block the eyes of the viewer in synchronism with the projected images so that the viewer's left eye receives only left eye images and the viewer's right eye receives only right eye images.

11. Apparatus as claimed in claim 9, wherein said means for separating the respective sets of images comprises means for alternately projecting images from the respective sets and optical shutter means for each viewer that block the eyes of the viewer in synchronism with the projection of the sets of images so that a viewer in each group sees only the images intended for that group, and wherein the means for presenting left eye images and right eye images comprises optical coding means for the images and corresponding optical decoding means for the viewers adapted to permit the right eye of each viewer to receive only correspondingly coded right eye images and the left eye of each viewer to receive only correspondingly coded left eye images.

12. Apparatus as claimed in claim 9, wherein said means for alternately projecting images comprises first and second projection means provided with mutually extinguishing polarizing filters, and wherein the optical decoding means provided to the viewers comprise correspondingly polarized filters arranged so that the right eye of each viewer can receive right eye images from the first projection means only and the left eye of each viewer can receive left eye images from the second projection means only.

13. Apparatus as claimed in claim 12, wherein the optical shutter means are electro-optic shutters incorporating said polarizing filters comprising the optical decoding means worn by the viewers.

14. Apparatus as claimed in claim 9, wherein said means for projecting respective sets of images comprises separate projectors and wherein said optical decoding means comprising mutually extinguishing filters for the respective projection means, and wherein the optical decoding means comprising correspondingly polarized filters worn by the viewers so that each viewer can see images projected by only one of the said projection means.

15. Apparatus as claimed in claim 14, wherein said optical shutter means are electro-optic shutters incorporating said polarizing filters.

16. Apparatus as claimed in claim 12, wherein each of said projection means comprises an electronic display projector.

17. Apparatus as claimed in claim 14, wherein each of said projection means comprises an electronic display projector.