Television – Holographic
Reexamination Certificate
1999-04-19
2001-03-13
Le, Vu (Department: 2713)
Television
Holographic
C348S051000, C348S054000, C359S028000, C356S457000, C396S288000
Reexamination Certificate
active
06201565
ABSTRACT:
TECHNICAL FIELD
The invention relates to a method and apparatus for displaying three-dimensional images, in particular moving images based on video signals containing three-dimensional image information. The invention may be used in all fields of displaying images.
When a planar image is produced on a surface, the light emitted or reflected from each point of the surface in any direction has approximately the same intensity (and colour). This is the working principle of a written sheet of paper (based on reflection) or a traditional television image (based on emission). But displaying a spatial image, the light emitted from a point of the surface in different directions have different intensity (and colour). This is the working principle of a window-pane regarded as a “display”, or that of a hologram. In short, for producing spatial images there is needed a light emitting surface, where the intensity (and colour) of the light emitted from a point of the picture, i. e. a pixel, may be controlled, depending on the exit angle, that is, the intensity of the light may be controlled in the different emitting directions.
BACKGROUND ART
Solutions to produce spatial images with laser technology, such as holograms, stereograms, etc. are known. It is a shortcoming of the known laser systems that they are inadequate for producing three-dimensional images from video signals. A method and apparatus for producing three-dimensional pictures is known from the International Patent Application published under WO 94/23541. This specification discloses two basic methods for producing three-dimensional images.
According to a first version of this known solution, the modulated laser beams are subjected to deflection according to the directions defining a field of view, and controlled in time, so that the modulated laser beam impinges on a predetermined pixel deflected, with a given entry angle, or parallel displaced, and exits from the pixel deflected or without further deflection, according to a predetermined direction defining the field of view. A disadvantage of this solution is that the laser beam needs very precise focusing and positioning, because the direction of the exiting laser beam is determined by the entry point within the pixel.
According to the other version, the modulated laser beam arrives at the pixel without any deflection within the entry points, and the time-resolved deflection, dependent of view directions is effected with controllable active optical elements, placed in each pixel. The angle deflection, dependent of the intensity, is performed by the active optical element. An advantage of this solution is that less precise focusing and positioning is needed, but a further disadvantage is that the active optical elements make the apparatus very expensive.
Hence it is an object of the invention to provide a method and apparatus for producing three-dimensional images, enabling to produce three-dimensional images using video signals containing three-dimensional image information, and this without the need for using expensive focusing and positioning elements. It is a further object of the invention to provide a method and apparatus for producing three-dimensional images, where a high-resolution screen does not contain expensive active beam deflecting elements, and which may be manufactured economically.
DISCLOSURE OF THE INVENTION
To achieve the above mentioned goals, we have found that a method for producing a three-dimensional image, comprising the steps of:
simultaneously modulating a—preferably spatially coherent—light beam by a video signal containing three-dimensional image information; and
directing the modulated light beam to pixels (image points) defining a first light emitting surface;
emitting a component of the light beam from the pixels within a predetermined angle of view (field of view) in the different view directions, with an intensity corresponding to the three-dimensional image,
directing the modulated light beams to the pixels from different entry angles, depending on the emitting angles within the angle of view, would provide a good basis for the invention.
According to the invention, this method should include directing the light beams modulated corresponding to the different directions to the pixels of the first light emitting surface from one or more light emitting points of a second light emitting surface, said second light emitting surface being spaced apart with a predetermined distance from the first light emitting surface. Essentially with this solution the functions of the first light emitting surface. practically the screen, are separated, and only the horizontal deflection and the vertical dispersion or divergence is performed on the first light emitting surface, while the light beams necessary for the creation of the image are produced and controlled at the second light emitting surface.
A preferred version of the method according to the invention includes selecting the number of the light emitting points and the number of light beams (the angle resolution) emitted therefrom in such a manner, that their product is equal to the product of the number of pixels and the number of directions (the angle resolution) into which light beams are emitted from the pixels. With this provision the displays may be produced economically, and have a good resolution, because the pixels defining the image resolution can be arranged in a large number on the first light emitting surface, and the number of directions contributing to the three-dimensional effect may be selected appropriately large, while at the same time a relatively small number of light emitting means are sufficient on the second light emitting surface, provided that their angle resolution is sufficiently large. The number of the light emitting points is at least one, according to the invention.
A further method of the invention includes simultaneously modulating the light beams emitted in the same direction from the pixels and associated with different pixels with light information associated with the same direction, and modulating the light beams of the light emitting points corresponding to the different emitting directions of the same pixel with the light information corresponding to the different view directions of the same pixel.
In a preferred example, the steps of the method include selecting the light emitting angle of the light emitting points of the second light emitting surface equal to the view angle (field of view) of the pixels of the first light emitting surface. In this case no angle correction is needed from the light emitting points to the eye watching the display.
In another preferred embodiment the steps include selecting the light emitting angle of the light emitting points of the second light emitting surface smaller or larger than the view angle (field of view) of the pixels of the first light emitting surface. In this case a further step will be necessary, namely applying angle correction on the light emitting angle of the light emitting points between the light emitting points and the pixels, or applying angle correction on the view angle (field of view) of the pixels, within the pixels themselves.
In a further, particularly advantageous version, a mirror is foreseen to deflect into corresponding pixels the light beams of the light emitting points emitted in directions bypassing the pixels of the first light emitting surface. This provision saves the need to install further light emitting points to illuminate the pixels on or close to the edge of the screen.
To realise the object of the invention, there is also foreseen an apparatus for displaying three-dimensional images, comprising a light source modulated with video signal containing three-dimensional information, and a deflecting system controlled in time and directed towards the pixels of a light emitting surface, wherein the light emitting surface is comprising one or more optical means transmitting and/or deflecting light beams in different directions within a predetermined field of view (view angle), and the deflectin
Frommer William S.
Frommer & Lawrence & Haug LLP
Holografica
Le Vu
LandOfFree
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