CA2107127C

CA2107127C - An apparatus for generating three-dimensional images

Info

Publication number: CA2107127C
Application number: CA002107127A
Authority: CA
Inventors: Burkhard Katz; Susan Kasen Summer
Original assignee: DIMENSIONAL MEDIA ASSOCIATES Inc
Current assignee: DIMENSIONAL MEDIA ASSOCIATES Inc
Priority date: 1992-01-28
Filing date: 1993-01-28
Publication date: 2001-01-16
Anticipated expiration: 2013-01-28
Also published as: DE4202303C2; WO1993015431A1; ES2118241T3; DE59308369D1; JPH06509885A; EP0577829A1; JP3121015B2; CA2107127A1; DE4202303A1; AU3452193A; ATE164948T1; EP0577829B1

Abstract

An apparatus for generating three-dimensional images of objects, characterized by two concave mirrors that are arranged opposite each other, with at least one area of the rear concave mirror being visible from a fixed observation area that is located in front of the front concave mirror, the front concave mirror being so arranged that the object that is either bright in and of itself or illuminated can be seen by way of the rays that emanate from the object and which are reflected between the two concave mirrors in the area of the rear concave mirror that can be seen from the observation area.

Description

AN APPARATUS FOR GENERATING THREE-DIMENSIONAL IMAGES
The present invention relates to an apparatus for generating three-dimensional images.
An object of the present invention is to provide an apparatus of this kind that, as viewed by an observer, a three-dimensional image appears to float freely in space in front of the apparatus, and can thus be combined with 1o actual objects or persons. A feature of the three-dimensional images that float freely in space, is that they can be enlarged or reduced to a certain extent, and can be superimposed over or faded into actual objects or persons.
Apparatus for generating a three-dimensional image of an object according to the present invention includes a fixed observation area and a stage. A first (front) concave mirror is adjacent to the observation area, and a second (rear) concave mirror is located away from the observation 2o area, with the reflecting surfaces of the two concave mirrors facing one another. The first concave mirror has a partial area which is transparent so that at least a partial area of the second concave mirror can be seen from the observation area. The first concave mirror is located in such a way that a virtual image of an object disposed between the two concave mirrors is projected onto the stage so that it can be combined with real objects or persons located there.
3o The object that is to be projected, which is preferably disposed close to the second (remote or rear from a viewer's standpoint) concave mirror, is reflected in the first (adjacent or front) concave mirror and the image is projected onto the rear concave mirror which can be seen by the observer. The distortion of the first reflection is eliminated as a result of the second concave mirror which preferably has the same radius of curvatures the image that is viewed by the observer is sharp and appears to the observer to be formed at a considerable distance in front of the surface of the rear concave mirror.
The concave mirrors can be slightly elliptical or 1o parabolic. An image that is especially free of distortion results if two spherical concave mirrors of the same radius of curvature are used.
If the concave mirrors are in the form of a spherical cap and their centres lie on one axis, and if the object that is to be projected is arranged in the vicinity of this axis close to the surface of the rear concave mirror (as viewed by the observer) and if a viewing aperture is located in the front concave mirror, close to the axis, then the 2o three-dimensional image will be visible from all sides in a cone-shaped area. Using such an apparatus, it is possible, for example, to display advertising images in store windows or on buildings or in open areas, to a large number of spectators.
Depending on the dimensions of the apparatus, the area that is visible to the observer can be so large that the object can move within it. In this way, animated objects or live persons can be projected and the apparatus can be used for 3o all types of presentations or theatrical performances, as well as for special effects in movie making.

2 The three-dimensional image can be either enlarged or reduced by changing the position of the concave mirrors relative to each other, for example, by axial displacement or by tilting one of the two concave mirrors. If the sur-faces of the mirrors are moved away from each other, the image can be enlarged to a certain extent; if the surfaces of the mirrors are moved closer together, the image becomes smaller. A similar effect can also be achieved by moving the object. If the object moves towards the surface of the 1o front concave mirror, it appears enlarged on the other hand, if it moves away from the surface, it is reduced.
The radius of curvature of the mirror has to be suffi-ciently large in order that this change in the size of the image does not cause troublesome distortion. On the other hand, this enlargement and reduction can be used to good effect in order to achieve special effects.
Generally speaking, it is preferable that the radius of 2o curvature of the concave mirrors is at least five times greater than a maximum extent of the object whose image is to be projected, a height of a spherical cap forming the concave mirror is at least 1.2 times as great as that extent, a cap diameter of the concave mirrors is at least six times greater than that extent, and a diameter of the viewing aperture is at least 1.5 times as great as the maximum extent.
If the apparatus is used in theatres or for concerts, when 3o the audience is located only within a specific angular range in front of the stage, it is sufficient if the concave mirrors in the apparatus form only portions of a spherical cap. This brings about a considerable reduction

3 in the space required for the apparatus, which is quite large, especially for forming images of people. Black walls should be adjacent to the peripheral edges of these concave mirrors and these, together with the concave mirrors, can form an essentially enclosed space so that no unwanted reflections are projected by the concave mirrors towards the observers. If the concave mirrors can be moved relative to each other by means of hydraulic mechanisms or other means, in order to exploit the enlargement or reduc-io tion effects, or if they can be pivoted by such means, then these walls should be either in the form of bellows and move with the mirrors or, in the case of a purely axial movement or a pure pivoting movement of the concave mirrors, they should be so configured that the mirror lies tight against the walls in any position.
The sources of light that illuminate an object that is to be projected and which is not bright in and of itself, can either be arranged in the area in front of the apparatus 20 (as viewed by the observer) or be arranged in areas of the apparatus that cannot be seen by the observer, for example, directly around the viewing aperture, or around the edges of the concave mirrors. The object itself can be illumin-ated both directly and also by way of reflections in the concave mirrors. The image can be made unfamiliar and the quality of the images can be influenced by selection of the light sources, for example, lights or laser light that can be varied with respect to beam width, colour, shape, and direction. The sharpest images are formed by illumination 3o using coherent white laser light. If the sources of the laser light are in a scanner that can vary the direction of the laser beam and is computer-controlled, then in addition

4 to this effect, laser show effects can be generated with the help of this device and then can be projected.
In addition to the projection of images of actual objects and persons, it is of course possible to project the images onto viewing screens. Because the apparatus for projecting the images has to be inclined for a viewing public on one level, it can be useful to arrange the objects that are to be projected on a flat area and reflect them into the 1o projection apparatus by way of a plane mirror.
It is advantageous to conceal the projection apparatus from direct viewing by the spectators. To this end, a semi-transparent screen can be arranged in front of the projec-tion apparatus (as viewed by the spectators). The object must be illuminated with sufficient power in order that the spectators can still view the three-dimensional image through the semi-transparent screen. The outside of the apparatus as well as of the concave mirrors, should be kept 2o as dark as possible in order that they cannot be seen through the semi-transparent screen. The most effective concealment for the projection apparatus will result if the semi-transparent screen is opaque in its edge areas and the transparency of the screen increases continuously in an inward direction, so that the greatest transparency is found in the area in front of the viewing aperture.
The semi-transparent screen can be between the viewing aperture and the imaging region in which the three-dimen-3o sional image appears to be located, or it can be within the image area. In the second case, the three-dimensional image appears to penetrate the wall that is formed by the semi-transparent screen.

If a mirrored semi-transparent screen is used, the three-dimensional image will appear in front of the reflected background, e.g., the black observation area, although it may form no reflected image in this screen itself.
If the semi-transparent screen is not mirrored, or if one surface is mirrored and the other is not but is partially diffuse, pictures or films can be projected onto it by means of a projector; these can then be combined with the 1o three-dimensional image. When this is done, the brightness of the light from the projector and from the object that is to be projected have to be so balanced that both the picture or the film and the three-dimensional image are clearly visible to the spectator.
Additional features of the present invention will be apparent from the following description of several specific embodiments of the invention, taken in conjunction with the accompanying drawings, in which:
2o Figure l: a perspective drawing illustrating the principle behind the apparatus according to the present invention;
Figure 2: a side view of an embodiment of the apparatus, that is integrated into a theatre;
Figure 3: a side view of a further embodiment with concave mirrors that can be tilted relative to each other;
Figure 4: a view of the front concave mirror as in Figure 3, as seen from below;
3o Figure 5: a side view of one embodiment of the apparatus with a semi-transparent screen.
The drawings that are described serve to illustrate operating principles of the apparatus and are not to scale.

The relationships, in particular between the object that is to be projected, the curvature of the concave mirror, and the distance between the concave mirrors, are to be adapted to each particular and specific application.
The apparatus that is shown in Figure 1 consists of two hemi-spherical concave mirrors 2, 3 of which the front (first) one 2 (from a viewer's standpoint) incorporates a viewing aperture 6. An observer can see an annular area of 1o the rear (second) concave mirror 3 in an angular area 4 that is conical, within which the object 5 that has been placed in the apparatus is reflected by the front concave mirror 2. Because of the fact that both concave mirrors 2, 3 have the same radius of curvature, abberations in the reflections cancel each other out. Because of the doubled reflection in a spherical concave mirror, a three-dimen-sional image 1 of the object 5 is formed for the observer, and this appears to be located at a considerable distance in front of the rear concave mirror 3, in the area of the 2o viewing aperture 6. Given the appropriate type and quality of the mirroring on the concave mirrors 2, 3, the image will appear to be absolutely real. The image of an object that is located close to the surface of the lower concave mirror 3 in the area of its axis of rotation 7 appears to be all but distortion-free. A coin lying in the area of the axis 7 on the surface of the concave mirror 3 would, for example, appear at actual size in the viewing aperture 6 when viewed by the observer.
3o If the three-dimensional image 1 that is generated is to be combined with an actual object, the viewing aperture 6 can be covered with a glass plate 8, on which actual objects can be placed.

The embodiment of the invention that is shown in Figure 2 is used in order to provide for the clearest and least distorted image of large objects, such as, for example, actors. The concave mirrors 12, 13 have a radius of curva-ture that is between 10 and 20 m. In order that the appa-ratus can be integrated structurally into a theatre or a stage, the bulged areas of the sphere will be eliminated from the spherical caps that form the concave mirrors 12, 13. Here, the concave mirrors 12, 13 form what is more or less the upper or lower third of a hemisphere so that given a sphere radius of 10 m, a maximum extent of 6 m will result for the superimposed concave mirrors 12, 13.
Figure 2 also shows an object stage 16 which is used to accommodate the object 5' whose image is to be projected.
That part of the stage 16 that cannot be seen from the observation area 4' is preferably black, in order that it radiates no unwanted light. The area of the stage 16 that is within sight of the observation area 4' is to be trans-2o parent in order that reflection is not disrupted.
Depending on the purpose for which the apparatus is used, this stage 16 can be made so that it can be pivoted, rotated, moved, or raised or lowered by means of suitable drive means.
The hydraulic cylinders 15 with which the front concave mirror 12 is articulated on the supporting frame 14 make it possible to change the axial distance between the concave mirrors 12, 13, by which means it is possible to vary the 3o size of a projection 1'.
The viewing aperture 6' within the area of which the projection 1' appears to stand, as viewed by the observer, is integrated into a stage 17. In order to permit unrestricted combination of the three-dimensional image 1' with actual objects, a part of the stage 17 extends into the viewing aperture 6'. This part is to be transparent in order that it does not cover that area of the rear concave mirror 13, in which the three-dimensional image 1' is formed. The spectator seating area 19 is situated facing the viewing aperture 6', in the viewing area 4'.
1o The whole apparatus has to be tilted relative to the hori-zontal in order that the three-dimensional image 1' can be seen by all the spectators in the viewing area 4'. The greater the inclination of the axis of rotation 7' of the concave mirrors 12, 13 relative to the vertical, the flat-ter the spectator seating 19 may be made. A versatile device will incorporate mechanical or hydraulic means by which this inclination can be varied.
A light source 20 is arranged in the area close to the 2o viewing aperture 6' behind the front concave mirror 12, as seen by the observer. The object 5' whose image is to be projected can be illuminated by this light source, either directly or by reflected light.
Since in a theatre only part of the cylindrically-shaped observation area 4' is filled with members of the audience and it is possible to see into only the part of the second concave mirror 13 which faces the audience and enables the reflections in the rear part of the first concave mirror 12 3o to be seen, it is possible to dispense with the front portion of the projecting device.

Figure 3 shows an embodiment of the apparatus in which only portions of spherical caps form the concave mirrors 22, 23, and Figure 4 is the front concave mirror 22 as seen from below in inverted plan view.
The installed size of the apparatus is further reduced by eliminating that part of the concave mirrors 22, 23 that cannot be viewed. In this embodiment, the concave mirrors 22, 23 are arranged so as to pivot about an axis 25. A
1o winch 27 is arranged on a platform 26 on the supporting frame 14' and the cable 28 is secured to the front concave mirror 22. The front concave mirror 22 can be tilted relative to the rear concave mirror 23 by using this winch.
This results in the enlargement and reduction effects of the three-dimensional image 1" that has been described heretofore. There is scarcely any distortion of this image since both concave mirrors are of identical radius of curvature at each point.
2o A blind 24 can be arranged in front of the viewing aperture 6" in order to cover a direct view of the object to be projected from the observation area 4", and it can be deployed and retracted automatically, if desired.
In this embodiment, light source 20' is arranged in an edge region of the front concave mirror 22.
The partial area of the spherical cap that forms the hollow mirrors can be further reduced depending on the appli-3o cation. In the inverted plan view of the front concave mirror 22 that is shown in Figure 4, the part 29 of the spherical cap that can, for example, be used for an apparatus which is essentially right in front of the observers is indicated by a dashed line. The partial area 30 that is indicated by the dashed and dotted line in Figure 4 is suitable for an apparatus that is to be viewed only from a fixed point of observation, such as the~loca-tion of the camera when a movie is being shot. The open areas between the concave mirrors 12, 13, 22, 23 of the apparatuses shown in Figures 2 and 3 are to be closed off with preferably black wall material (not shown in the drawings) in order to prevent the ingress of troublesome 1o incident light. Light-proof black material, bellows devices, or even rigid black walls suitable for this purpose if the concave mirrors 12, 13, 22, 23 do not have a particularly large degree of freedom relative to each other.
Projection is not confined to fixed objects moving live or animated objects can also be projected. In this case, the projection apparatus is to be designed so as to take the anticipated area of movement of the object into account.
In addition, images that are projected onto viewing screens, such as television images, transparencies, films, or laser projections, can also be shown. In the event that the angle of inclination of the axis 7', 7" of the appa-ratus is too great in an apparatus for projecting images to an audience that is seated horizontally, the object that is on a horizontal stage can be reflected into the apparatus by a plane mirror that is arranged in the vicinity of the axis 7', 7", close to the rear concave mirror 13, 23.
It is important that the concave mirrors are of a precisely spherical shape in order to achieve optimal image quality.
In addition, the mirrors should be mirrored on their surfaces, because an additional transparent layer between the object and the mirrored surface could cause double reflections, interference, and distortion. At least one sub-region of the viewing aperture can be covered by a semi-transparent concave mirror whose reflecting surface lies on a spherical surface with the first concave mirror.
Figure 5 shows the apparatus as shown in Figure 3 combined with a stage 17 for actual objects and persons, and a semi-to transparent screen 31 that covers the device from direct view from the observation area 4". The semi-transparent screen 31 can be extended between the ceiling and the stage 17.
The upper edge area 32 of the transparent screen 31 is opaque, as is indicated by the hatching. The transparency of the screen 31 increases in an inward direction, so that the greatest transparency of the screen 31 is directly in front of the viewing aperture 6". The object that is to be 2o projected must be illuminated with sufficient strength by the light source 20' so that the three-dimensional image 1"
can be seen through the screen 31.
A film projector 33 is installed in front of the screen 31 and this projects a film image onto the screen 31 in the area of the viewing aperture 6". If the power of illum-ination of the object that is to be projected is stronger in the apparatus than the light strength of the image that is projected by the projector 33, then the three-dimen-3o sional image will appear to be in front of the projected image.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. An apparatus for generating a three-dimensional image of an object, the apparatus having a fixed observation area and a stage; a first concave mirror adjacent to the observation area and a second concave mirror remote from the observation area, the reflecting surfaces of the two concave mirrors facing one another; the first concave mirror having a transparent partial area so that at least a partial area of the second concave mirror can be seen from the observation area; and the first concave mirror being disposed in such a way that a virtual image of an object disposed between the two concave mirrors is projected onto the stage to be combined with real entities located there.

2. Apparatus according to claim 1, in which the concave mirrors are spherical and have the same radius of curvature.

3. Apparatus according to claim 1 or 2, in which the centres of the spherical surfaces of the concave mirrors are disposed substantially on the same axis of rotation.

4. Apparatus according to claim 1, 2 or 3, in which the concave mirrors are in the shape of a spherical cap with a peripheral edge, the first concave mirror in the region of its axis of rotation having a viewing aperture as the transparent partial area, and said object is disposed in the region of the axis of rotation of the second concave mirror.

5. Apparatus according to claim 4, in which the radius of curvature of the concave mirrors is at least five times greater than a maximum extent of the object whose image is to be projected, a height of a spherical cap forming the concave mirror is at least 1.2 times as great as said extent, a cap diameter of the concave mirrors is at least six times greater than said extent, and a diameter of the viewing aperture is at least 1.5 times as great as said extent.

6. Apparatus according to claim 5, in which the radius of curvature and the cap diameters of the concave mirrors are 10 to 20 m, the height of a cap is 2 to 4 m, and the diameter of the viewing aperture is 4 to 6 m.

7. Apparatus according to claim 4, 5 or 6, in which the concave mirrors are portions of spherical caps.

8. Apparatus according to any one of claims 4 to 7, in which the concave mirrors are arranged with their edges superimposed one on the other.

9. Apparatus according to any one of claims 4 to 7, in which the concave mirrors are spaced apart from one another.

10. Apparatus according to claim 9, in which the peripheral edges of the concave mirrors abut tightly against black walls, which together with the concave mirrors form an enclosed area.

11. Apparatus according to any one of claims 1 to 10, in which the concave mirrors are mounted on a supporting device so as to be adjustable relative to one another.

12. Apparatus according to any one of claims 1 to 11, in which the concave mirrors are mounted on a supporting device so as to be adjustable relative to a horizontal position.

13. Apparatus according to any one of claims 4 to 12, in which at least one of the concave mirrors is mounted so that it can pivot about an axis.

14. Apparatus according to claim 11, 12 or 13, including drive means which can effect pivoting and adjusting motion of at least one of said concave mirrors.

15. Apparatus according to any one of claims 4 to 14, including at least one blind preventing the object to be projected from being visible directly from the observation area.

16. Apparatus according to claim 15, in which the blind can be extended and retracted automatically.

17. Apparatus according to any one of claims 4 to 16, in which an object stage for accommodating the object whose image is to be projected is disposed in a region of said axis of rotation.

18. Apparatus according to claim 17, in which said object stage can be pivoted, rotated, displaced or raised and lowered.

19. Apparatus according to any one of claims 4 to 18, in which a light source for illuminating said object is disposed in front of said viewing aperture.

20. Apparatus according to any one of claims 4 to 18, in which a light source for illuminating said object is disposed in an edge region of said viewing aperture on the reflecting inward-facing surface of said first concave mirror.

21. Apparatus according to any one of claims 4 to 18, in which a light source for illuminating said object is disposed in an edge region of said concave mirrors.

22. Apparatus according to any one of claims 4 to 18, in which a light source for illuminating said object is disposed in an edge region of said front concave mirror.

23. Apparatus according to any one of claims 4 to 18, in which a light source for illuminating said object is disposed, viewed from said object, behind semi-transparent regions of said concave mirrors.

24. Apparatus according to any one of claims 19 to 23, in which the light source is a spotlight whose beam width, colour, shape and direction can be computer controlled.

25. Apparatus according to any one of claims 19 to 23, in which the light source is a laser.

26. Apparatus according to any one of claims 19 to 23, in which the light source is a collimator with a diffuser disposed in front, the collimator being secured in a scanner and connected by an optical waveguide to a laser.

27. Apparatus according to any one of claims 19 to 23, in which the light source is a collimator with a prismatic optical system disposed in front, the collimator being secured in a scanner and connected by an optical waveguide to a laser.

28. Apparatus according to any one of claims 1 to 27, in which said object is a viewing screen.

29. Apparatus according to any one of claims 1 to 28, in which said object is a plane mirror, and an article to be imaged is disposed in such a manner behind said second concave mirror as to be visible from said observation area in the plane mirror via the concave mirrors.

30. Apparatus according to any one of claims 1 to 29, in which the concave mirrors are mirror surface-coated.

31. Apparatus according to any one of claims 1 to 30, in which at least one sub-region of said viewing aperture is covered by a semi-transparent concave mirror whose reflecting surface lies on a spherical surface with the first concave mirror.

32. Apparatus according to any one of claims 1 to 31, in which a semi-transparent screen is disposed between said first concave mirror and said stage.

33. Apparatus according to claim 32, in which said semi-transparent screen is opaque at its edge regions and its transparency increases continuously in an inward direction so that its area of maximum transparency is in front of said viewing aperture.

34. Apparatus according to claim 32 or 33, including a projector for projecting images onto said semi-transparent screen.

35. Apparatus according to claim 32, 33 or 34, in which said semi-transparent screen is a semi-transparent mirror.