WO2005062106A1

WO2005062106A1 - Projection apparatus for display of images floating in space

Info

Publication number: WO2005062106A1
Application number: PCT/HU2004/000115
Authority: WO
Inventors: Róbert KUPPER
Original assignee: Kupper Robert
Priority date: 2003-12-22
Filing date: 2004-12-13
Publication date: 2005-07-07
Also published as: EP1702231A1; HU226569B1; HU0304103D0; HUP0304103A2

Abstract

Projection apparatus (1) for display of images floating in space comprising a concave mirror positioned in a housing (2). Within the housing (2) an image generating apparatus (4) is placed angularly to the main optical axis (X) of the concave mirror. The housing (2) is provided with an opening (5) formed on a side opposite the light-reflecting surface (6) of the concave mirror, and the opening (5) is closed by a partly light-absorbing, partly light-transmitting and partly light-reflecting window (7). The concave mirror is an elliptic mirror (3).

Description

Projection apparatus for display of images floating in space

The invention relates to a projection apparatus for display of images floating in space, the apparatus comprises a concave mirror positioned in a housing, within the housing an image generating apparatus is placed angularly to the main optical axis of the mirror, the house is provided with an opening formed on a side opposite the reflecting surface of the mirror, and the opening is closed by a partly light-absorbing, partly light- transmitting and partly light-reflecting window. The invention further relates to a projection apparatus for display of images floating in space comprising a partly light- transmitting plate and a concave mirror positioned in a housing, within the housing an image generating apparatus is placed, and the house is provided with an opening formed on a side opposite the reflecting surface of the mirror, and the opening is closed by a partly light-absorbing, partly light-transmitting and partly light-reflecting window. In the last decade more and more holographic projectors have become known in the art. Examples of such projection systems include patent applications 679342 A5 (Switzerland), US 4,802,750, US 5,311,357, US 5,552,934, US 2003/0053033 Al and US 6,598,976 B2.

The first four of the aforementioned patent applications relate to apparatuses applicable for projection of objects which are positioned in the apparatus and lighted with spotlights. Patent application US 2003/0053033 describes an aerial projection system and method having a housing for positioning low cost optical elements capable of generating three dimensional aerial images at video rates without reflected artifacts or visible display of the display screen. The method for generating the display images eliminates boundary transgessions and maximizes the illusion of a three dimensional aerial image. An optional second display is a transparent imaging panel that acts selectively as a light valve, as a display platform for special effects or for providing the appearance of linear motion towards or away from the observer. An optional third display, also a transparent imaging panel, may be used as a background display device for displaying video rate images that are not projected aerial images. According to the solution proposed here an image transmitted by a display device is projected by means of a special monitor, a beam splitter and a polarizer arranged parallel with the beam splitter. A condition of functioning of the apparatus according to this document is to. achieve a background color of (0,0,0) which is impossible with the presently known techniques. Application of the spherical mirror in case of maintaining a defined visibility angle limits the distance between the displayed floating image and the window of the apparatus. Patent application US 6,598,976 B2 describes a real image projection system which comprises a single curved mirror having two different optical surfaces of revolution, one on the convex surface and one on the concave surface. In one embodiment, the convex surface is a conical curve of spherical or parabolic surface of revolution coated with a reflective optical coating. The concave surface is much like that of a Mangin mirror, but it has an aspheric surface of revolution optimized to reduce spherical aberrations over a larger area offset from the optical axis. The system optionally employs a single aspheric surface of revolution on the concave surface for reduction of aberrations, although the Mangin mirror approach, using an aspheric concave surface of revolution is the preferred embodiment. The apparatus according to this document employs two image display devices and two mirrors. The two image display devices are symmetrically separated from each other by a beam splitter. The beam passing through the beam splitter and the reflected beam reach the surface of the first then the second mirror with a phase shift. This phase shift and imperfections in the surfaces of the two mirrors have negative influence on the quality of the displayed image. The aim of the present invention is to provide a projection apparatus which can be constructed in a simple manner, which is suitable for display of a good quality floating image in the possible furthest distance, and in which the number of refractive objects to be placed in the path of the light beams for producing a floating image is minimized. The inventors have realized that the floating image may be displayed at a greater distance from the projector when an elliptic mirror (having two focuses) is used. The light beams emerging from the image generating apparatus (display device) may be directed onto the surface of the mirror directly so that they will not shade the path of the beams reflected from the surface of the mirror to the other focus, consequently use of a display device with normal luminance (e.g. a monitor) may be satisfactory. In addition, use of a refractive plate may be necessary only in certain cases, then an easily producible glass plate having a partly light-transmitting surface may serve as the refractive plate.

In a first aspect the projection apparatus for display of images floating in space according to the invention comprises a concave mirror positioned in a housing. Within the housing an image generating apparatus is placed angularly to the main optical axis of the concave mirror. The housing is provided with an opening formed on a side opposite the reflecting surface of the concave mirror, and the opening is closed by a partly light-absorbing, partly light-transmitting and partly light-reflecting window. The concave mirror is an elliptic mirror.

In a second aspect the projection apparatus for display of images floating in space according to the invention comprises a partly light-transmitting plate and a concave mirror positioned in a housing, within the housing an image generating apparatus is placed. The housing is provided with an opening^' formed on a side opposite the reflecting surface of the concave mirror, and the opening is closed by a partly light- absorbing, partly light-transmitting and partly light-reflecting window. The concave mirror is an elliptic mirror, and in the center line of the partly light-transmitting plate a shaft is disposed, in this way rotation of the plate becomes possible. The shaft is positioned perpendicular to the main optical axis of the mirror. Preferably, the housing is formed of two parts, the first part containing the image generating apparatus, the second part containing the projector unit. Advantageously, the image generating apparatus comprises a computer and one or more display devices, the projector unit comprises the mirror and the window, and in a certain case, the plate. The elliptic mirror may be manufactured as a sandwich structure having a highly accurate elliptic shape made up of a mirror plate placed in between two glass plates which are separated by means of a fusion preventive medium. During manufacture programmed heat effect is applied, and after removal of the two glass plates a light-reflecting layer is formed on the reflecting, concave surface of the mirror plate by applying an inoxidizable metallic material. In order to produce several floating images simultaneously, several display devices may be placed within the projection apparatus, several windows may be formed in the second part of the housing, and the focal distance and the curvature of the mirror are selected suitably for display of several floating images. Advantageously the shaft of the plate is positioned on a shaft supporting member to make rotation of the plate possible.

The projection apparatus for display of images floating in space according to the invention will now be described in more details with reference to the accompanying drawings in which: Figure 1 is a perspective front- view of the apparatus according to the invention; Figure 2 is a sectional plan view of the first part of the apparatus of figure 1 taken along line II-II;

Figure 3 is a sectional plan view of the second part of the apparatus of figure 1 taken along line UI-III;

Figure 4 is a partial sectional side view of the second part of the apparatus;

Figure 5 is a partial sectional side view of the apparatus provided with the plate when the plate is adjusted to outward projection of an image;

Figure 6 is a partial sectional side view of the apparatus provided with the plate when the plate is adjusted to project an image inwardly, i.e. behind the apparatus;

Figure 7 is a partial sectional plan view of the second part when two display devices are used;

Figure 8 shows the layout of the glass plate layers forming the mirror during manufacture; and Figure 9 shows a portion of the finished mirror.

Projection apparatus 1 consists of two parts (figure 1). The first part 10 (figure 2) contains an image generating apparatus 4 comprising for example a computer 13 and its accessories, and a display device 14 which is preferably a monitor. The advantage of constructing the image generating apparatus 4 in this manner is that they can be manufacttired and installed separately, and also, in case of possible failure they can be easily serviced.

Second part 11 contains mirror 3 and its support 19, and an opening 5 is formed on a side of the second part 11 opposite the light-reflecting surface 6 of mirror 3. In opening 5 a partly light-absorbing, partly light-transmitting and partly light-reflecting window 7 is placed (figure 3). In a certain case a plate 8 having a partly reflecting, partly light- transmitting surface and provided with a shaft 9 supported by a shaft supporting member 17 is also placed in second part 11 (figure 5). This arrangement makes rotation of plate 8 around shaft 9 possible, i.e. the angle between surface of plate 8 and the main optical axis X can be varied. Use of plate 8 is reasonable when display device 14 can not be directed directly to mirror 3 (figure 5), or when a projected image 18 is not to be displayed outside the projection apparatus 1 before window 7, but rather, display is required deep in projection apparatus 1 behind mirror 3, apparently in a distance exceeding the size of projection apparatus 1 (figure 6). This may be possible when image 18 is not projected by the reflecting surface of plate 8 towards mirror 3, but towards window 7, thus towards the viewer. Otherwise image 18 will appear floating before window 7 in a distance determined by the optical features of the component parts of projector unit 12. Light-absorbing nature of window 7, appropriate lighting of the environment exterior to projector unit 12 and the dark background of the image displayed on display device 14 collectively guarantee the sharpness of the displayed image and also the imperceptibility of mirror 3 in the background. A function of window 7 is to block out the components used for producing an image and at the same time to ensure a homogeneous background which is free from disturbing elements. When window 7 is omitted, image 18 is still viewable, but in this case interfering effects of the background are perceptible to the eye.

In the embodiment according to figure 4 display device 14 is not parallel with the main optical axis X, thus the image to be projected is transmitted directly onto mirror 3. Then, as it can be seen in the figure, the distance of display device 14 relative to the main optical axis X, and also the angle between the surface of display device 14 and the main optical axis X can be varied. The distance, the size and the visual angle of the displayed floating image 18 from window 7 covering opening 5 of the second part 11 depend on the size of the used elliptic mirror 3, the positions of its focuses as well as the location of the source of the image to be projected by means of interposition of directly or indirectly reflecting surfaces. In order to produce image 18 transmitted by projection apparatus 1 at a defined distance from window 7 outside housing 2 the focal distance of mirror 3 and the measurements of housing 2 are determined. With elliptic mirror 3 used in the present invention a wider range of action is ensured than with spherical mirrors used in the prior art. By using elliptic mirror 3 and by appropriate positioning of several display devices 14 it is possible to display two floating images 18 simultaneously (figure 7). Display device 14 (e.g. a monitor) may directly transmit the image to be displayed to elliptic mirror 3 (figure 4). An elliptic mirror 3 has the following advantages as compared to a spherical mirror: display device 14 may be directed directly onto the surface of mirror 3 so that it will not shade the path of the beams reflected from the surface of mirror 3 and proceeding towards the other focus. Consequently use of a display device 14 with normal luminance (e.g. a monitor) may be satisfactory. For proper display of an image it is not necessary by all means to use a prism which absorbs a portion of the light. Image generating apparatus 4 including display device 14 may be operated by a software running on a known operating system (LINUX, WINDOWS) of computer 13. Operating may take place locally or it may be remote controlled, individually or in a network. Image generating apparatus 4 enables the user to run his own-made material on computer 13 independently of the fact that display of another image is possibly programmed in computer 13. Also, a digital camera may be coupled to image generating apparatus 4 which may produce a floating image of a viewer. It is important for computer 13 to display the projected images with a background as dark as possible. At the same time computer 13 is adapted for correcting possible deformation of a displayed image 18.

In order to produce an image of a good quality in a known method for manufacturing the elliptic mirror 3 the following steps are taken: mirror plate 20 is placed in between two glass plates 15 and a fusion preventive medium 16 is applied between the adjacent surfaces to separate them. This sandwich structure is then shaped to have a highly accurate elliptic form by applying programmed heat effect. Next, the glass plates 15 are removed and a light-reflecting surface 6 is formed on mirror plate 20. The light- reflecting surface 6 is a layer made of an inoxidizable metallic material. The base material of the light-reflecting surface 6 is inoxidizable metal, e.g. titanium. Since during production of the image display device 14 transmits the image directly or at most with the interposition of plate 8 onto the light-reflective surface, the image forming light beams proceed through window 7 into the air-space with the least possible reflection. In this way deformation resulting from the inaccuracy of the surfaces participating in producing floating image 18 maybe eliminated or reduced.

Claims

1. Projection apparatus (1) for display of images floating in space comprising a concave mirror positioned in a housing (2), within said housing (2) an image generating apparatus (4) is placed angularly to the main optical axis (X) of said concave mirror, said housing (2) is provided with an opening (5) formed on a side opposite the light- reflecting surface (6) of said concave mirror, and said opening (5) is closed by a partly light-absorbing, partly light-transmitting and partly light-reflecting window (7), characterized in that said concave mirror is an elliptic mirror (3).

2. Projection apparatus (1) for display of images floating in space comprising a partly light-transmitting plate (8) and a concave mirror positioned in a housing (2), within said housing (2) an image generating apparatus (4) is placed, said housing (2) is provided with an opening (5) formed on a side opposite the light-reflecting surface (6) of said concave mirror, and said opening (5) is closed by a partly light-absorbing, partly light- transmitting and partly light-reflecting window (7), characterized in that said concave mirror is an elliptic mirror (3), and in the center line of said partly light-transmitting plate (8) a shaft (9) is disposed in order to make rotation of said plate (8) possible, said shaft (9) is positioned perpendicular to the main optical axis (X) of said mirror (3).

3. Projection apparatus according to claims 1 or 2 characterized in that said housing (2) is formed of two parts, a first part (10) containing said image generating apparatus (4), and a second part (11) containing a projector unit (12).

4. Projection apparatus according to any of the previous claims characterized in that said image generating apparatus (4) comprises a computer (13) and one or more display devices (14).

5. Projection apparatus according to any of the previous claims characterized in that said projector unit (12) consists of said mirror (3) and said window (7), and in a certain case said plate (8).

6. Projection apparatus according to any of the previous claims characterized in that said elliptic mirror (3) is manufactured as a sandwich structure made up of a mirror plate (20) placed in between two glass plates (15), said plates (15, 20) are separated by means of a fusion preventive medium (16), and are shaped to have a highly accurate elliptic form by applying programmed heat effect, and after removal of said two glass plates (15) a light-reflecting surface (6) is formed on the reflecting, concave surface of the mirror plate (20) by applying an inoxidizable metallic material.

7. Projection apparatus according to any of the previous claims characterized in that in order to produce several floating images (18) simultaneously, several display devices (14) are placed within said projection apparatus (1), several windows (7) are formed in said second part (11) of said housing (2), and the focal distance and the curvature of said mirror (3) are selected suitably for display of several floating images (18).

8. Projection apparatus according to any of claims 2-7 characterized in that said shaft (9) of the plate (8) is positioned on a shaft supporting member (17) to make rotation of the plate (8) possible.