Optical: systems and elements – Deflection using a moving element – Using a periodically moving element
Utility Patent
1998-06-08
2001-01-02
Phan, James (Department: 2872)
Optical: systems and elements
Deflection using a moving element
Using a periodically moving element
C359S202100, C359S204200
Utility Patent
active
06169621
ABSTRACT:
BACKGROUND OF THE INVENTION
a) Field of the Invention
The invention is directed to an apparatus for generating an image on a screen by illuminating image points in a plurality of partial images by means of light bundles, wherein the apparatus has at least one deflection device for deflecting a plurality of light bundles in respectively associated image points of the individual partial images, and a control device for controlling the intensity of the light bundles depending on the brightness of the respective image point to be illuminated, and optics between the screen and deflection device for transforming the light bundles in a partial image associated with the respective light bundle.
b) Description of the Related Art
Projection devices of the type mentioned above are dimensioned, on the one hand, for flat large-area projection screens, for example, in stadiums or cinemas, and, on the other hand, for cylindrical-wall or spherical-wall, dome-shaped screens, for example, for simulators or planetaria.
Large-area image displays which give the observer the impression of being surrounded by space are required especially for planetaria, but also for flight simulators. As evidenced by the success of the presentations in the planetarium in the Forum der Technik in Munich, dome projections of films and laser shows appeal to a large segment of the population, so that it is expected that an entirely new area of entertainment can be opened up given suitable economical technical solutions.
At present, a substantial difficulty with regard to the projection of the images mentioned above consists in the generation of a sufficiently high luminous density because, assuming a spectator space of the same size, a surface to be covered by a projection is substantially greater than a conventional cinema screen, for example. Therefore, a remedy for projecting an image has been sought in the independent projection of partial images in individual contiguous screen segments from which a total image is formed. However, the films which must be used in this case have a very large format due to the high illumination density and the consequent thermal loading. Furthermore, they are also difficult to handle for this reason. In spite of the large film sizes, projectors in current use always require elaborate cooling measures.
For this reason, this type of projection has not been introduced before in cinema technology for showing a two-hour film, for example, apart from isolated instances such as projection devices at public festivals offering only short films at a commensurate price.
Further, projection in a plurality of partial images creates problems for reasons of geometry particularly with respect to the division of a spherical projection surface into a plurality of image segments.
Planar imaging on a curved surface without distortion is impossible. Further, there are always overlapping areas when projecting partial images, for example, when the projected image is delimited by straight edge areas. This problem can be solved by distorting the image to be projected on the film itself, for example, in order to compensate for the geometric distortions, and by cutting off in the overlapping area. Specially processed films for dome projection are required in this case. This is also a big cost factor which has so far restricted commercial utilization.
WO 95/01061 describes a projection system in which a light beam is deflected by means of X-Y scanners and projected in a dome as vector graphics by means of a projection system comprising lens arrays. In this arrangement, the deflecting mirrors are arranged one behind the other in the beam path and are controlled in Cartesian coordinates.
In the book, “Der Himmel auf Erden, die Welt der Planetarien”, Ludwig Meier, Verlag Johann Ambrosius Barth, Leipzig-Heidelberg, 1992, pages 65 to 67, a dome projection is described, wherein the dome is filled with content by projecting an individual film. A fisheye lens is used to illuminate the partially spherical screen. However, this type of projection results in insurmountable distortions at the edge of the image. Further, because of the high thermal loading of the film by 12,000-Watt arc lamps, a cooling of the 70 mm film, already a large format, must be provided.
Moreover, the special production of a film with a running time of 30 minutes would cost in the region of several million U.S. dollars.
For a more economical management of distortions in the primary projected image, there are suggestions for image processing by means of computer which are described in detail on pages 70 ff. of the above-mentioned book. Pages 71-75, for example, describe a planetarium in which stars are shown on a picture tube in an electronically controlled manner. The image contents generated on the screen of the picture tube are subsequently projected again in the dome with a fisheye lens system.
Cinema films could also be projected on a dome in the same manner with a system of this kind. However, current computer performance for distortion of the image so that these images can be projected on the dome via the fisheye lens system so as to be restored to their geometrically correct state are inadequate.
It is further suggested on pages 70 and 71 of the above-mentioned book to display images with lasers by means of raster scanning on the curved screen as in the example of electron beam tubes. However, experiments in this direction have not led to commercial success owing to the low available laser output, the required high writing speed to the screen, and the resulting poor resolution taking into account conventional switching speeds for controlling intensity.
For smaller partially spherical surfaces, on the other hand, a laser device of the type mentioned above is known from U.S. Pat. No. 4,297,723, in which an image is displayed on a partially spherical screen surface in three separate sectors by raster scanning. To display the image in the image segments illuminated by three partial images, three light bundles are combined by means of a mirror system, directed by optics onto a raster scanning device jointly shared by all of the partial images, and then separated again by means of further optics and subsequently deflected onto the screen in the individual image segments by additional expansion optics.
However, the combination of the laser beams on practically one point of the deflection device and subsequent separation requires highly precise adjustment. This disadvantage is particularly critical when it is considered that the illumination of a large, hemispherical screen, for example, requires substantially more than three image segments to be illuminated, so that the effort for adjustment of the mirror systems and optics which would be required for this purpose would no longer be realizable in practice.
OBJECT AND SUMMARY OF THE INVENTION
Therefore, it is the primary object of the invention to provide an apparatus for the illumination of a plurality of partial images of an image which substantially avoids the disadvantages mentioned above. In particular, adjustment expenditure in this apparatus is greatly reduced.
Based on the prior art mentioned above, this object is met in that the optics include an entrance pupil which is spread out over an extended area and an exit pupil which is much smaller in comparison to the entrance pupil, and in that a plurality of deflection devices for deflecting a light bundle associated with a partial image are provided in or near the entrance pupil which is spread out over an extended area or are formed therein.
Therefore, the optics used in accordance with the invention differ from the optics known from U.S. Pat. No. 4,297,723, for example, in that the large area of an entrance pupil is imaged in a very small, practically punctiform exit pupil and a plurality of deflection devices are arranged in or in the vicinity of the entrance pupil of these optics or are formed therein. Because of this characteristic of the optics, a raster region generated in the entrance pupil is then always transformed into a partial ima
Deter Christhard
Hiller Klaus
Roeder Rolf
Carl Zeiss Jena GmbH
Phan James
Reed Smith LLP
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