BACKGROUND OF THE INVENTION So-called"immersive experience"motion picture theatres attempt to provide audience members with the perception that they are "immersed"in the images that are being shown. Typically, such theatres are relatively small and are designed to provide an intimate theatre environment. Often, 3-D motion pictures are shown, sometimes on a dome screen. Dome screens in particular give audience members the perception of being"within"the environment represented by the projected images. Large format dome screen 3-D images such as those that are shown in IMAX SOLIDO@ theatres, are particularly effective in providing a realistic immersive theatre experience.

Special techniques are required to produce motion pictures that satisfactorily can be projected in 3-D on a dome; accordingly, production costs are high. Considering those costs, and the fact that only a relatively small number of dome theatres are capable of showing the films, the selection of available films is relatively restricted.

An object of the present invention is to provide a motion picture theatre structure and a method of presenting motion picture images that are capable of providing an immersive motion picture experience. In particular, the theatre structure and method of the invention may allow showing in a novel immersive environment, of 3-D motion pictures that were produced for projection onto conventional flat screens. In other words, the objective is to achieve a dome-like immersive experience using motion pictures that were shot for flat screens.

SUMMARY OF THE INVENTION One aspect of the present invention provides a motion

picture theatre structure including a screen, an audience seating deck which slopes downwardly towards the screen, and at least one projector located within the seating deck for projecting images onto the screen about an optical projection axis which is angled upwardly with respect to the horizontal. The screen is arcuate as seen in plan and is positioned symmetrically with respect to the projection axis of the projector and so as to wrap around respective sides of the seating deck. The screen also slopes upwardly towards and extends above the seating deck for providing the audience with a sense of immersion in images projected onto the screen.

The projector is provided with a wide angle lens with low centre-of-field distortion, for example an orthographic fisheye lens. An orthographic fisheye lens can be designed to substantially fill the screen with projected images, while minimizing distortion of centre regions of the images.

Another aspect of the invention provides a method of presenting motion picture images to audience, comprising the steps of: providing: a screen which has an arcuate shape as seen in plan; an audience seating deck which slopes downwardly towards the screen; and at least one projector located within the seating deck for projecting images onto the screen about an optical projection axis which is angled upwardly with respect to the horizontal; positioning the screen (a) symmetrically with respect to the projection axis as seen in plan so that said arcuate shape wraps around respective sides of the seating deck and (b) sloping towards and extending above the seating deck, whereby the audience is provided with a sense of immersion in images projected onto the screen; and, projecting images onto the screen from said at least one projector using a wide angle lens with low centre-of-field distortion, for example an orthographic fisheye lens, for substantially filling the screen with projected images and providing an immersive viewing experience.

In summary, the present invention provides an immersive theatre experience in that the screen wraps around and extends above the seating deck so as to essentially fill the field of view of audience members

in much the same way as a dome screen, except that the screen does not extend behind the viewer. At the same time, by using a lens such as an orthographic fisheye lens on the projector, distortion in the central portion of the image is minimized and in a sense"pushed out"to the periphery of the image, where it becomes much less significant in terms of viewer perception, particularly for 3-D presentations.

Theatres in accordance with the present invention may be designed as new"immersive experience"theatres or as modifications or "retrofits"to existing dome theatres. In either event, the resulting theatre will be capable of showing a wide range of films irrespective of whether those films were initially shot for showing in dome theatres or more conventional flat screen theatres. For example, an IMAX@ theatre in accordance with the present invention would be capable of showing the full range of IMAX@ 3-D films whether shot initially for"normal" IMAGO or IMAX SOLIDO@ theatres, and whether in 2-D or 3-D format.

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 a preferred embodiment of the invention by way of example, and in which: Fig. 1 is a perspective view of a theatre structure in accordance with a preferred embodiment of the invention; Fig. 2 is a plan view of the theatre structure shown in Fig. 1; Fig. 3 is a side elevational view; Fig. 4 is a reproduction of a photograph taken through an orthographic fisheye lens for the purpose of illustrating the characteristics of the lens; and, Fig. 5 is a diagrammatic front elevational view of a projector for use in the theatre structure of the invention.

DESCRIPTION OF PREFERRED EMBODIMENT Referring first to Fig. 1, the interior of a theatre is shown as seen from above and to one side of the rear of a seating deck 20 of the

theatre, looking towards a curved projection screen 22. Images projected onto screen 22 are represented at 24 and are projected from a projector 26 located within the seating deck 20. External walls of the theatre are represented at 28.

Figs. 2 and 3 show schematically, the overall configuration of the theatre including external walls 28, the seating deck 20, screen 22 and projector 26. In these views, the theatre is shown"as designed", although it is to be understood that the theatre structure of the invention could be achieved by modifying or"retrofitting"an existing theatre, such as a 3-D dome theatre. In that case, the screen 22 would be assembled inside the existing building.

Fig. 3 shows that the seating deck 20 slopes downwardly towards the screen 22 and that the projector 26 projects images onto the screen 22 about an optical projection axis 30 which is angled upwardly with respect to the horizontal (32). It will be seen that projector 26 is in fact located within a projection room 34 that is built into the seating deck amid upper ones of the rows of seats (see Fig. 3); images are projected through a window 36 in the projection room.

As best seen in Fig. 1, the screen 22 has an arcuate shape as seen in plan (see Fig. 2). The projection axis 30 referred to in connection with Fig. 3 is also indicated in Fig. 2 and it will be seen that the screen 22 is positioned symmetrically with respect to the projection axis as seen in plan, and is arranged to"wrap around"respectively opposite sides of the seating deck 20. From that view and from Fig. 3, it will be seen that the screen also slopes upwardly towards and extends above the seating deck.

In summary, the screen wraps laterally around and extends above the seating deck; this provides the audience with a sense of immersion in the images projected onto the screen.

In this particular embodiment, screen 22 has the shape of a segment of a cone which tapers towards the upper end of the screen and is tilted towards the seating deck as described previously to provide the desired wrap around immersive environment. In order to optimize the

characteristic of the reflected light, the angle of tilt of the screen is selected so that the optical axis of projection 30 meets the screen generally at a right angle ( 10°) on the vertical centreline of the screen C (Fig. 2). In this case, the angle of tilt (=--Fig. 3) is approximately 15° with respect to the vertical.

The vertical height of screen 22 (in this embodiment 60 feet) is selected to match the characteristics of the projection lens L of projector 26 in terms of the vertical extent of the projected image.

Similarly, the lateral extent of screen 22 (see Fig. 2) is selected to match the horizontal extent of the projected image, which is in this case about 150°. Compared with a theoretical angle of 180° for a full dome screen, it will be seen that there is some loss of extent of the projected image, though the amount is not believed to be significant in terms of audience experience since the loss is in the viewer's region of peripheral vision only.

The projection lens of projector 26 (L--Figs. 2 and 3) is an orthographic fisheye lens. Fig. 4 is a representation of a photograph taken through such a lens and illustrates the fact that distortion in the centre region of the image is minimized to a greater extent than with a conventional fisheye lens and is, in effect,"pushed out"towards peripheral regions of the image. This is evident from Fig. 4 in that the lines delineating the edges of buildings are straight in centre regions of the image and curve to progressively greater extents towards the perimeter of the image. In the application of the present invention, this means that the projected images tend to be true in front of the viewer and that distortions occur in the regions of the peripheral vision of the viewer, where they are much less noticeable. Orthographic lenses are well-known in the art and have been available from Nikon under the trade mark NIKKORTM.

Characteristics of orthographic lenses are described in"Applied Photographic Optics"by Sydney F. Ray first published 1988 by Focal Press-- London and Boston. As described in Ray, an orthographic lens is defined by the formula y = 2f sin (@/2) or y = f sin (3

where f equals focal length, y equals image height, e equals semi-object field angle (rad) in object space.

It should here be noted that, while Fig. 4 is illustrative of an orthographic fisheye lens, it is not intended to represent the precise characteristics of an optimum fisheye lens for use in the method of the present invention.

As indicated previously, the method and theatre structure of the present invention are applicable to presentation of both 2-D and 3-D motion pictures. Where 3-D motion pictures are to be projected, respective sets of"left-eye"and"right-eye"images must be projected and optically coded, for example, by using mutually extinguishing polarizers or by projecting the images alternately. The viewers must then wear eyeglasses designed to decode the images so that the viewer's left eye sees only left-eye images and the right eye only right-eye images. Both polarizer and"alternate eye"techniques for effecting such coding and decoding are well-known in the art. Preferably, the alternate eye technique is used in the method of the invention.

While two projectors may be used, a single projector for projecting both sets of images is preferred. For example, a rolling loop projector of the type shown in United States Patent No. 4,966,454 (Toporkiewicz) may be used. The disclosure of this patent is incorporated herein by reference. Basically, the projector has two superposed rolling loop mechanisms, one of which projects the left-eye images while the other projects the right-eye images. The respective sets of images are projected through superposed lenses generally as shown in Fig. 5. In that view, the two rolling loop mechanisms are denoted 46 and 48 and the respective lenses associated with two mechanisms are denoted 50 and 52.

U. S. Patent No. 4,997,270 (Shaw) which is also incorporated herein by reference, discloses an arrangement for performing a programmed"lens shift"to correct for abnormalities in the print from which the images are being projected. In the method of the present invention, a similar technique may be used to optimize presentation of

the projected images, for example to compensate for the fact that the film may originally have been shot for showing on a flat screen. In such a case, the position of the center of interest within images will have been chosen with the geometry of a typical flat screen theatre in mind. Typically, the centre of interest of these images will appear near the vertical mid-point on a flat projection screen. In an immersive theatre, such images will appear too high on the screen for audience seated in the front rows. Thus, in order to change the vertical position of the image as projected to shift the centre of interest to co-incide with the best viewing point on the screen, the two lenses, 50 and 52 may be moved together up or down through the same incremental amount. Such movement should be programmed in real time to correspond with scenes in the film being projected, all generally as described in the Shaw patent supra.

Similarly, the lenses 50 and 52 can be programmed to change the"parallax"of the image, i. e. to move the image towards or away from the audience by effecting relative shift of the lenses inwardly or outwardly.

Both lenses may be shifted (both outwardly or both inwardly) or only one lens may be shifted while the other lens is kept stationary. Again, this lens shift would be programmed in real time to follow the images on the film.

In Fig. 5, vertical shift of both lenses to change the centre of interest of the projected image is represented at 54 and horizontal shift to adjust the image parallax is represented at 56 as movement of the lower lens 52.

The actual mechanisms by which the lenses are shifted may be designed in accordance with the teachings of the Shaw patent supra. In one embodiment, the two lenses are carried on a common carriage 58 that can be moved vertically by a rotary actuator 60 with respect to a lens mount M. At the same time, lens 52 is supported on carriage 58 for horizontal movement under the control of a rotary actuator 62. The two actuators 60 and 62 are operated by a controller 64 that responds to "witness"marks on one of the two films via a reader 66.

In summary, the-method and structure provided by the invention allows creation of an immersive motion picture experience by

means of a theatre structure that is less costly than a conventional dome theatre but which at the same time produces a very similar motion picture experience. An existing dome theatre can be converted in accordance with the invention at relatively low cost by installing a curved screen as screen 22 and providing the projector with an orthographic fisheye lens as described previously. The theatre can then show a complete range of motion pictures whether originally shot for dome screens or for conventional flat screens.

It should be noted that the drawings of the preferred embodiment included herein illustrate the invention in schematic terms only and that precise details may vary within the broad scope of the invention. For example, the theatre structure itself has been shown only very schematically in Figs. 2 and 3 and may vary according to the particular preferences of the theatre architect and the environment. The screen 22 preferably has the shape of a segment of a cone as discussed previously, but alternatively could have the shape of a segment of a cylinder. The screen structure is preferably a space frame carrying a vinyl screen material which is painted with a highly reflective paint, all as well-known in the art.

However, other screen configurations could be used, for example, segmented rigid screens.