WO1998011737A1

WO1998011737A1 - Method and apparatus for presenting a visual display to an audience

Info

Publication number: WO1998011737A1
Application number: PCT/CA1997/000653
Authority: WO
Inventors: Gordon W. Harris; Kevin Kowalchuk; David M. M. Dean; Albert W. Darimont
Original assignee: Imax Corporation
Priority date: 1996-09-09
Filing date: 1997-09-05
Publication date: 1998-03-19
Also published as: AU4195597A; CA2264887A1

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

Title: METHOD AND APPARATUS FOR PRESENTING A VISUAL DISPLAY TO AN AUDIENCE

FIELD OF THE INVENTION

This invention relates to a method of presenting a visual display to an audience. The invention has been devised primarily (but not exclusively) in connection with so-called "immersive" wide field-of-view displays. In this context, the term "immersive" means that the viewer experiences a high sense of realism or "immersion" in the display, for example, as in a virtual reality environment. BACKGROUND OF THE INVENTION

A number of approaches currently are used to provide an exciting and immersive visual environment for entertainment purposes. One such approach makes use of large film format motion picture equipment such as that supplied by Imax Corporation to provide high resolution images which completely fill a viewer's field of view. Visual cues which may remind viewers that they are watching a motion picture are effectively removed, thereby creating a sense of immersion or involvement in the action being depicted on the screen.

The sense of immersion can be further enhanced by projecting stereoscopic large format motion pictures onto a wide field of view screen. The large viewing angles associated with such a screen greatly increases the stereoscopic viewing space in which 3-D objects can be positioned and viewed. Several methods of presenting stereoscopic images currently are used; the most common are polarization and electronic "alternate eye" separation of images. In polarization stereoscopic projection, linear polarizer filters are placed respectively in front of left eye and right eye projectors with their polarizing axes at 90 degrees to each other. Viewers wear eyeglasses with polarizing filters arranged 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 only the left eye polarized light is transmitted through the left eye lens of the eyeglasses and only the right eye polarized light is transmitted through the right eye lens.

In electronic alternate eye stereoscopic projection, left-eye and right-eye images are presented alternately so that there is only one eye image on the screen at any moment in time. Viewers wear glasses which alternately block the view of one eye so that only the correct images will be seen by each eye. The glasses typically have electro-optic liquid crystal shutters and are powered by batteries. 3-D motion picture systems of this type 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 the performance 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 disclosed in Canadian Patent Application No. 2,146,811 filed April 11, 1995. All of these references have been assigned to Imax Corporation. Their disclosures are hereby incorporated by reference.

The sense of realism or immersion of a display can be enhanced by providing for interaction between audience members and the display system so that the audience members have some degree of control over what they are seeing. Usually this kind of user control is restricted to single viewer displays only, such as those known as head mounted displays (HMD's). A viewer wearing a HMD is completely immersed in the display. However, because of technology limitations, in practice, the viewer can only see a very low resolution image. Another disadvantage of HMD's is that the viewer is completely isolated visually from other participants, 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 by Iwerks under the trade mark "VIRTUAL ADVENTURES" in which a small 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 or viewport. This restricts the visual field of view provided to the participants. The narrow field of view translates to a limited stereoscopic or 3-D space and the sense of immersion is compromised. Another disadvantage of such a system is that the narrow field of view restricts the placement of audience members within the vehicle simulator. As a result, some audience members are seated in good viewing locations while others are located in poorer viewing locations. The result is a lack of experience equality for all members of the audience which can lead to disappointment for some participants. DESCRIPTION OF RELATED ART

There are several examples of multiple point of view displays in the prior art:

U.S. Patent No. 5,260,729 to Ullah et al. discloses an apparatus and method for displaying non-interfering color images to two or more viewers. A first set of images is generated from a first set of color wavelengths and a second set from a second set of color wavelengths. The two sets of wavelengths are spectrally multiplexed to include first and second red, green and blue wavelengths. A first viewer views the images through a filter which transmits the first set of wavelengths, but rejects the second set of wavelengths. A second viewer views the images from a filter which transmits the second set of wavelengths but rejects the first set of wavelengths.

U.S. Patent No. 4,879,603 to Berman discloses a multiple image single display apparatus and method. A monochromatic display source provides first and second sets of images which alternate rapidly. The images pass through an active polarization assembly which polarizes all of the images of the first set to a left handed circular polarization and all of 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 which reflects left-handed polarized light. U.S. Patent No. 4,657,512 to Mecklenborg discloses a display system for a vehicle simulator which allows two individuals to see images correct for their point of view in front of a curved projection screen. Two projectors are used; a left-handed circular polarizer filter is placed in front of one and a right-handed circular polarizer is placed in front of the other. Two separate windshields are provided, each of which has a circular polarizer filter placed in front so that the images from a first one of the projectors are transmitted by a first windshield and not a second windshield, and the images from the second projector are transmitted by the second windshield and not the first windshield. SUMMARY OF THE INVENTION

The present invention is based on the realization that there is a need for a visual display system which allows multiple points of view and social interaction between groups of viewers (audience groups). Preferably, the system should be both visually immersive and provide for an engaging, interactive group experience.

In one aspect, the invention provides a method of presenting a visual display to an audience, comprising the steps of: providing for each of two groups of viewers a projection screen, a projector for projecting a set of images onto that screen and a point of view for the group of viewers in front of that screen; and locating the respective points of view and the viewing screens so that the groups of viewers are located in close proximity to one another and the viewing screen for each group of viewers is located outside the field of view of the viewers of the other group.

Preferably, the display is a wide-field of view stereoscopic display that provides multiple unique points of view simultaneously to multiple groups of participants in such a manner that each group can only see the set of images intended for them and not any of the other sets of images associated with other groups. The unique and exclusive point-of- view of each group allows for independent interaction. The display can be a shared computer generated virtual environment. The expression "point of view" as used in the present disclosure 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 to the physical location or attitude of the viewers. References to two groups of viewers having different points of view means that each viewer in any one group sees the same images and that those images are different from the images seen by the viewers in the other group. For example, the two points of view may be represented by images from a common scene or environment, but seen from different perspectives or vantage points.

The projectors preferably are electronic display projectors. It should be understood that, wherever this term is used in the disclosure and claims, it is intended to be interpreted broadly as including a wide range of electronic projection systems having different resolution and image quality characteristics. Included within this term are graphics projectors typically having resolutions up to 2000 x 2000 pixels, data projectors for use with personal computers having resolutions up to 1024 x 768 pixels, high definition television projectors (HDTV) providing up to 1125 lines with an aspect ratio of 16,9, and video projectors suitable for suitable NTSC resolution (typically 380 - 480 lines). Reference may be made to "Electronic Displays: Technology, Design and Applications" Gerry C. Whitaker, McGraw-Hill, New York, 1994 for further discussion of display projectors. A second aspect of the present invention provides a method of presenting a visual display to an audience, comprising the steps of: providing two points of view for two groups of viewers; projecting onto a viewing screen visible from both points of view, 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.

In one preferred embodiment of this aspect of the invention, first and second electronic display projectors and one projection screen are provided. The first projector has a first linear polarizer filter in front of its lens, with the polarization axis in one direction. The second projector has a second linear polarizing filter in front of it's lens oriented at 90 degrees with respect to the axis of the first polarizing filter. Viewers in a first audience group wear electronic alternate eye glasses which have linear polarizers on the front surface of the lenses oriented to transmit images from the first projector but to block images from the second projector. Similarly, viewers in a second audience group wear electronic alternate eye glasses which have linear polarizers on the front surfaces of their lenses which are oriented to transmit images from the second projector and block images originating from the first projector. Each projector alternately projects left and right eye images in synchronism with the opening and closing of the liquid crystal shutters in the electronic alternate eye glasses.

In an alternative embodiment, the left and right shutters of the glasses are opened and closed simultaneously and each group's glasses being driven out of phase so that while one groups' shutters are both open, the other audience groups' shutters are both closed. In such a configuration, a first projector projects the left eye images for a first audience group and the right eye images for a second audience group, and a second projector projects the right eye images for the first audience group and the left eye images for the second audience group.

Either embodiment allows each audience group to see full stereoscopic wide field-of-view unique images while simultaneously looking at the same screen at the same time. The two audience groups can be located in close physical proximity thereby allowing stimulating visual and verbal interaction between the two groups. In addition, because the two groups are located closely together, each participant will have roughly equal fields of view of the screen resulting in a perception of experience equality among all participants.

A still further aspect of the invention provides a method of presenting a visual display to an audience, comprising the steps of: providing at least two points of view for at least two groups of viewers; projecting onto a viewing screen visible from said at least two points of view, respective sets of images, one for each group of viewers; and, separating the respective sets of images 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, providing each viewer with electro- optic shutter means that alternately block and expose the eyes of the viewer, and timing said shutter means in synchronism with the projection of the images, so that each viewer sees only the images intended for his or her group.

An apparatus corresponding to each method aspect of the invention is also provided.

BRIEF DESCRIPTION OF DRAWINGS

In order that the invention may be more clearly understood, reference will now be made to the accompanying drawings which illustrate preferred embodiments of the various aspects of the invention, and in which:

Figs, la) and b) are respectively diagrammatic plan and side elevational views illustrating an arrangement of projectors, screens and audience groups in accordance with a first aspect of the invention;

Figs. 2 is a view similar to Fig. la) illustrating a further embodiment of this aspect of the invention;

Figs. 2a and 2b illustrate images that may appear on the screens in the embodiments of Figs, la) and b) and Fig. 2;

Fig. 3 is a view similar to Fig. la) illustrating a second aspect of the invention; Fig. 4 comprises a block diagram denoted a), which illustrates a system for projecting two independent sets of stereoscopic images onto a single projection screen as shown in Fig. 3, and diagrammatic illustrations denoted b) and c), which show the corresponding polarization of electronic glasses 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 projectors shown in Fig. 4;

Fig. 6 is a view similar to Fig. 4 and contains the same illustrations a), b) and c) for an alternative embodiment of this aspect of the invention;

Fig. 7 is a view similar to Fig. 5 but comprising six timing diagrams denoted respectively a), b), c), d), e), and f) for the embodiment of

Fig. 6;

Fig. 8 illustrates similar timing diagrams denoted a), b), c), and d) for a further embodiment of the invention in which images are presented to four separate audience groups; and, Fig. 9 is a further view illustrating timing diagrams denoted a), b), c), d), and e) for a still further embodiment of the invention in which separate points of view are presented to four groups of viewers using a single projector.

DESCRIPTION OF PREFERRED EMBODIMENTS Fig^s- 1 ⁿd 2 illustrate the first aspect of the invention referred to previously, in which there is provided, for each of two groups of viewers (audience groups), a projection screen, a projector for projecting a set of images onto that screen and a point of view for the group of viewers in front of the screen. The respective points of view and the viewing screens are located so that the groups of viewers are in close proximity to one another and the viewing screen for each group of viewers is located outside the field of view of the viewers of the other group.

Referring first to Figs. 1 a) and lb), a first electronic projector 20 projects images onto a projection screen 22. Seated in front of screen 22 is an audience group 24 consisting of two people. Similarly, a second electronic projector 26 projects images on projection screen 28 located in front of a second audience group 30. In the drawings, the points of view referred to previously are represented by the diagrammatic illustrations of people.

The projectors 20 and 26 preferably are high resolution projectors, capable of at least 1000 lines of vertical resolution. One such projector is available under the trade mark ELECTROHOME MARQUIS 3000. Though not essential to the invention, the projected images preferably are generated by a simulation computer thereby allowing realtime interaction between the audience groups and the images they see. Audience members are then provided with an input device such as a joystick or spaceball (not shown) with which they can enter commands, directions or selections to the simulation computer to affect a change in the simulated environment or their current point of view of the environment. These features may be provided in accordance with known techniques and accordingly are not described in detail here.

Audience groups 24 and 30 are arranged back to back so that they are still close together, within normal audible speech range of each other, and also so that only their own projection screen is visible.

Fig. 2 shows a similar embodiment but with the screens and audience groups located at right angles to each other. Primed reference numerals are used to denote elements that correspond with elements shown in Figs, la) and b). Of course, relative angular orientations are possible other than right-angular.

In either embodiment, the projectors may (but need not necessarily) display full colour stereoscopic images to each group by the alternate eye method of stereoscopic separation. In such a case, audience members would require electronic alternate eye glasses to properly receive the stereoscopic images, for example as taught in the references incorporated herein (supra). Since the images are exclusively presented to the respective audience groups, each group can have a completely independent view from that of the other group enabling separate and independent interaction with the simulation. The proximity of the audience groups allows for friendly social interaction between the two groups as the entertainment experience unfolds, which can involve either cooperation or competition between the two groups.

The images viewed by the respective groups of viewers may be related for enhancing interaction between the groups. Figs. 2a and 2b illustrate an example of such related images as seen by two viewer groups.

In a non-interactive experience, Group 1 viewers could be seeing a narrative from one point of view, say, the police. In the example illustrated, the viewers would see an overhead helicopter view of a fugitive's getaway car. Group 2 would see the narrative from the point of view of the fugitive in the getaway car.

In an interactive experience, team members would have control over the vehicles depicted on the screens through computer input devices connected to computers running a real-time simulation. Fig. 3 illustrates a second aspect of the invention, in which double primed reference numerals have been used to denote elements that correspond to elements shown in Figs, la) and b). Two electronic projectors 20" and 26" project images onto a single projection screen. Two audience groups 24" and 30" are located beside each other in front of screen 32. Each group sees a unique set of images. Although the audience members are shown in two side-by-side groups, they could in fact be located in any physical arrangement including an alternating arrangement such as team 1 - team 2 - team 1 - team 2 because the method of image separation is independent of audience location within the viewing zone. Referring to Fig. 4, a control computer 34 contains a database of all objects and events which define a simulated world or environment. The control computer regularly sends current information of the simulated environment to four graphics computers, 36, 38, 40 and 42, each of 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 a first audience group (group 24" in Fig. 3), while computer 38 renders images for the right eye of the same group. Similarly, computers 40 and 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 as those that have Pentium processors are sufficient for the purposes of maintaining and rendering the simulated environment. It has been found necessary to enhance the rendering computers with 3D graphics accelerators such as the "3Deamon" supplied by Omnicomp.

The data generated by computers 36 and 38 are transmitted to projector 20" (see also Fig. 3). A linear polarizing filter 44 is arranged in front of the lens of projector 20" with its polarizer axis horizontal (indicated by arrow "H"). Computers 40 and 42, likewise transmit data to electronic projector 22" which has a linear polarizer filter 46 arranged so that its polarization axis is vertical (arrow "V"). Viewers in the first audience group 24" members wear electronic liquid crystal shutter glasses 48, which have both of their outer linear polarizers oriented so that their polarizer axes are horizontal ("H") and thereby parallel to the axis of the polarizer 44 in front of projector 20". Likewise the viewers in audience group 30" wear electronic glasses 50 which have both of their outer polarizers oriented to be vertical and thereby parallel to the axis of the polarizer 46 in front of projector 22". The orthogonal linear polarizers in front of the lenses of the projectors effectively create two separate points of view when used with the corresponding glasses 48 and 50. Projectors 20" and 22" are driven to alternately project left and right eye images, and the images are alternately transmitted and blocked by the liquid crystal shutters of glasses 48 and 50, thereby allowing the simultaneous presentation of two separate stereoscopic points-of-view.

Suitable techniques for constructing and driving the shuttered glasses 48 and 50 are well-known to people skilled in the art and are discussed in some of the references incorporated herein. Liquid crystal shutters used in glasses for 3-D viewing each incorporate two linear polarizers on either side of a liquid crystal cell. The two polarizers are oriented with their axes orthogonal to one another and the liquid crystal - Im ¬

material acts as a variable polarizer influenced by an electric field. The polarizers may be appropriately oriented in constructing the glasses so that the outer polarizer is positioned to function in accordance with the method described herein. Fig. 5 illustrates the timing of the alternating images for projector 20". In Fig. 5a) one complete image "frame" is depicted by the line denoted 52, representing the time during which that frame is displayed. The frame consists of a left eye image LI, followed by a right eye image RI, followed by the same left eye image, followed by the same right eye image. The frame rate is typically 30 Hz in normal video applications, but because of the limitations of the graphics processing hardware the frame rate of the disclosed invention is typically 15-20 Hz. To avoid objectionable flicker it is necessary to present each image twice during one frame so that the flicker rate is elevated to 30-40 Hz. The duration of one flicker 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 the viewers in the first audience group (24"). The transmission of the shutter varies from 0 to 100% and is timed so that it is fully open when projector 20" is projecting a left eye image and fully closed when a right eye image is projected. 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 the linear polarizer 44 associated with projector 20 and of each shutter in the glasses of the audience group. The timing diagrams for the left and right eye shutters for the members of the second audience group will be the same.

To summarize, in the embodiment of Fig. 4, the sets of stereoscopic images that are intended for the first group of viewers are projected exclusively by the first projector, 20", and the left and right eye images within that set are separated from one another using the "alternate eye" technique. The same applies to the sets of images for the viewers in the second group. The viewers in the respective groups see only those images that are intended for that group because of polarizers 44 and 46 that are associated with the respective projectors and the correspondingly polarized glasses that are worn by the viewer groups.

In other words, the polarizers provide means for separating the respective sets of stereoscopic images and the "alternate eye" technique comprises means for presenting, within each set of images, the left eye images only to the left eye of the viewer, and the right eye images only to the right eye of a viewer in the relevant group.

Fig. 6 illustrates an alternative embodiment of the invention in which the techniques for separating the sets of images intended for the respective groups and the left eye and right eye images within those sets of images are reversed. In other words, in the embodiment of Fig. 6, the alternate eye technique is used to separate the respective sets of images for the two groups of viewers, and the polarizer technique is used to separate the left and right eye images within each set. Thus, the elements shown in Fig. 6 are the same as the elements shown in Fig. 5 (and are similarly designated). The only difference is that, in each pair of eyeglasses (48 and 50) the polarizer in the left eye lens is horizontally polarized and the polarizer in the right eye lens is vertically polarized, as indicated by the respective arrows denoted H and V. The computers 36, 38, 40 and 42 also generate the images differently. The computers 36 and 38 generate respectively the left eye images and the right eye images for the first group of 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 by computer 40, are projected by the second projector 22", whereas the right eye images for that same group of viewers are projected by the first projector 20".

Fig. 7 illustrates the timing for the embodiment of Fig. 6. In Fig. 7a) the output of the first projector 20" alternates between a left eye image for the first audience group and a right eye image for a second audience group. Similarly, Fig. 7b) shows that the output of the second projector 22" alternates between right eye images for the first audience group and left eye images for the second audience group. The arrows H and V at the left of the timing diagrams represents the orientation of the polarizers in front of the lenses of the first and second projectors.

Referring to Fig. 7a), the designation Ll_τ denotes the left eye image -- audience group 1 - frame 1 and R2₅ indicates the right eye image — audience group 2 - frame 1. In other words, the first integer is a letter designating left eye or right eye image, the second integer is a number indicating the first or second audience group and the subscript is a number indicating the particular frame in the sequence being displayed. Fig^s- 7c) and d) illustrate the timing of the opening and closing of the liquid crystal shutters in the glasses worn by the first group of viewers (24"). The timing is arranged so that the left and right eye shutters are opened and closed together in synchronism. Figs. 7e) and f) illustrate the timing of the shutters for the glasses worn by members of the second viewer group (30").

As can be seen in the diagrams, the respective sets of images are "time multiplexed" and are never projected onto the screen at the same time. The separation of left and right eye images within each set is accomplished by the orientation of the polarizers on the glasses and in front of each projector. An advantage of the Fig. 6 embodiment is that the amount of ghosting or cross-talk between the two audience groups images is noticeably less than is the case when polarizers are used for image separation. This is particularly useful since the ghosting between the audience groups views is often more noticeable and objectionable than is the case between left and right eye image ghosting.

In summary, using the embodiment of Fig. 4 or the embodiment of Fig. 6, respective sets of stereoscopic images can be projected onto the same viewing screen for two different groups of viewers. The viewers in each group do not see the images for the other group. The system may be passive or interactive. For example, viewers could be provided with input devices such as a joystick or spaceball as discussed previously in connection with Figs, la), lb) and 2 to effect a change in the simulated environment or their current point of view of the environment. In Figs. 4a) and 6a), input devices for the viewers of the two groups of viewers are represented at !^■■ and I₂ respectively. The respective groups of viewers could, for example, be given the sensation of driving different cars on the same road or on a racetrack, or playing hide-and-seek within a maze. While neither group of viewers would see the viewpoint of the other group, an indication of that viewpoint, for example, the position of the other "person" (for example the other driver in a race car situation or the other person in a maze) may be provided in the form of a graphical icon or "avatar" such as is typically used to represent the "other person" in virtual reality environments.

Fig. 8 shows timing diagrams presenting images to four separate audience groups in accordance with a further aspect of the invention. The large numbers 1 to 4 represent the images for the four groups and the subscripts represent the frame sequence (each frame is projected twice). Fig. 8a) shows that the images for groups 1 and 2 are time-multiplexed and projected by a first projector having a horizontally aligned 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 4 and 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 by groups 1 and 3 followed by groups 2 and 4 respectively.

Both lenses in the glasses worn by the viewers of groups 1 and 2 are horizontally polarized so that the viewers in those groups cannot see 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 are vertically 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 images for group 2 viewers are being projected, and vice versa. Similarly, both eyes of the viewers of group 3 are blocked when the images for group 4 are being projected, and vice versa. In other words, the images for groups 1 and 2 are separated from one another by time multiplexing and from the images of groups 3 and 4 by means of the polarizers. Similarly, as between groups 3 and 4, the images are separated by time multiplexing, and those images are separated from the images of groups 1 and 2 by the polarizers.

Fig. 9 illustrates another embodiment of the invention in which different two-dimensional images are presented to four groups of viewers using a single projector. As shown in Fig. 9a) an electronic projector projects four time-multiplexed fields or images in the same time that is normally used to present two fields or images. Each image is projected twice. The projector must necessarily have rapid turn on and off of the projected images to allow such multiplexing; projectors capable of this are those based on a digital mirror device (DMD) imaging chip such as those manufactured by Texas Instruments. Figs. 9b) - e) illustrate the timing of the liquid crystal shutter glasses for the four audience groups. In other words, in the embodiment of Fig. 9, the images for the four groups are projected from a single projector in time-multiplexed fashion and the glasses for the four groups of viewers are triggered in synchronism, so that the eyes of a particular viewer are unobscured only during the time for which the image intended for that group is on the screen. A second projector and orthogonal linear polarizer filters can be added to add either an additional four audience groups or to add stereoscopic images for the four initial groups.

While the present invention has been described herein with reference to particular embodiment, it is understood that the invention is not limited thereto. The teachings of this invention may be used by one having ordinary skill in the art to make modifications thereof. For example, although linear polarizers have been described as an element of the invention, circular polarizers could be used instead. Also, although the invention has been described in the context of a computer driven interactive experience the invention could be used with non-interactive passive displays originating from film, video, laser disk etc.

Also, while the claims refer specifically to two groups of viewers (audience groups), it is of course to be understood that, within technical limitations, multiples of two groups can be accommodated, as exemplified in the disclosure above.

Claims

WE CLAIM:

1. A method of presenting a visual display to an audience comprising the steps of: locating two groups of viewers comprising said audience within normal audible speech range of each other, each group having a respective point of view; providing for a first of said two groups of viewers, a first projection screen and a first projector for projecting a set of images onto that screen; providing for a second of said two groups of viewers, a second projection screen and a second projector for projecting a set of images onto that screen; and, locating the viewing screens with respect to the points of view so that the viewing screen for each group of viewers is located outside the field of view of the viewers of the other group.

2. 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.

3. A method as claimed in claim 2, 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.

4. A method as claimed in claim 2, 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.

5. A method as claimed in claim 4, 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.

6. A method as claimed in claim 3, 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.

7. A method of presenting a visual display comprising the steps of: providing an audience comprising at least two groups of viewers having respective points of view; providing a viewing screen visible from said points of view; projecting onto said screen, respective sets of images, one for each group of viewers; and, separating the respective sets of images 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.

8. A method as claimed in claim 7, 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.

9. A method as claimed in claim 8, 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.

10. 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.

11. Apparatus as claimed in claim 10, 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.

12. Apparatus as claimed in claim 10, 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.

13. Apparatus as claimed in claim 10, 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.

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

15. Apparatus as claimed in claim 10, 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.

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

17. Apparatus as claimed in claim 13, wherein each of said projection means comprises an electronic display projector.

18. Apparatus as claimed in claim 15, wherein each of said projection means comprises an electronic display projector.

19. Apparatus for presenting a visual display to an audience comprising at least two groups of viewers each having a point of view, the apparatus comprising: a viewing screen visible from said points of view; means for projecting onto said screen, respective sets of images, one for each group of viewers; and, means for separating the respective sets of images so that each group of viewers sees only the images intended for that group, said means comprising means for projecting the images from each set at intervals separated in time, and electro-optic shutter means for each viewer that alternately block and expose 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.