Optical: systems and elements – Single channel simultaneously to or from plural channels – By partial reflection at beam splitting or combining surface
Patent
1996-08-01
1999-01-19
Font, Frank G.
Optical: systems and elements
Single channel simultaneously to or from plural channels
By partial reflection at beam splitting or combining surface
356630, 356633, G02B 2714
Patent
active
058619933
DESCRIPTION:
BRIEF SUMMARY
This invention relates to apparatus for displaying an image of an object, comprising a beam splitter being positioned in a path for light from the object, and retroreflector means being positioned in a path for light from the object which has been reflected by the beam splitter.
Such an arrangement is disclosed in EP0460873 and in W087/00328. The image appears to be suspended in space and may appear to be three dimensional.
According to the present invention, there is provided an apparatus as defined in the first paragraph, characterised in that the retroreflector means comprises a plurality of retroreflective surfaces opposing one another such that the image may be viewed from a plurality of predetermined directions.
This apparatus may be used, for example, for displaying an image of a VDU above a table top, or for displaying an image of a dashboard display of a vehicle.
Embodiments of the invention will now be described, by way of example only, with reference to the accompanying diagramatic drawings, in which FIGS. 1, 2, 3 and 5 are included for the purposes of description only and are not within the scope of the present invention the Figures:
FIG. 1 is perspective view of an apparatus for displaying an image;
FIG. 2 is a cross sectional side view of the apparatus of FIG. 1;
FIGS. 3, 4 and 5 are cross sectional side views of alternative arrangements .
Referring to FIGS. 1 and 2, an opaque surface 2 such as a tabletop, shown broken away, includes a beamsplitter window 4 mounted in an aperture therein. In this embodiment, retroreflector means comprising an array of retroreflectors, such as a sheet 6 of corner-cubes, is positioned in a path for light which has been reflected by the beamsplitter 4. In this example it is positioned at an acute angle thereto, which is about 45.degree., so as to form the second side of a triangle therewith. An object 8 such as a picture displayed on a VDU screen is positioned along the third side of the triangle, in this example at about 90.degree. to the beamsplitter. Alternatively, the screen may be positioned parallel to the beamsplitter, or at any other orientation where light from the object reaches the beamsplitter. Other objects such as three-dimensional objects may also be displayed by the apparatus by placing them in an equivalent position.
In a preferred embodiment, means for screening the retroreflector 6 from the object is provided, such as a louvre film 12 in front of the object 8. As indicated by arrows in FIG. 2, the beamsplitter 4 reflects light from the object 8 towards the retroreflector 6. In addition some of the light is transmitted by the beamsplitter 4 and is `lost`. The beamsplitter 4 also transmits light reflected from the retroreflector 6 to form the suspended image 14 opposing the object 8 with respect to the beamsplitter 4. In addition, some of the light is reflected by the beamsplitter back towards the original image 8.
In the embodiment shown in FIG. 3, a further array of retroreflectors 16 is positioned in a path for light which has been transmitted by the beamsplitter. In this example, the further array opposes the retroreflector 6 with respect to the beamsplitter 4; that is, it forms a triangular arrangement with the beamsplitter 4 and the suspended image 14. The further array of retroreflectors 16 directs light which is transmitted by the beamsplitter 4 directly from the original image 8 back towards the beamsplitter 4 to prevent `loss` of this light. In an alternative embodiment of the invention, the array of retroreflectors 6 in a path for light which is reflected by the beamsplitter 4 could be omitted.
In the embodiment of FIG. 3, the object 8 is a projection screen, and an image is formed thereon by a projector 18. The projector 18 is shown positioned in the gap 10 between the retroreflector array 6 and the object 8, but may have other positions. For example it may be positioned in an aperture in the retroreflector array 6.
As indicated by plus and minus signs adjacent arrows in the Figure, the beamsplitter may be polarisation selective, tra
REFERENCES:
patent: 5583695 (1996-12-01), Dobrusskin
patent: 5585967 (1996-12-01), Monroe
Dobrusskin Christoph
Shanks Ian Alexander
Central Research Laboratories Limited
Font Frank G.
Ratliff Reginald A.
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