Optics: image projectors – Relief illusion
Patent
1994-08-25
1996-04-16
Dowling, William C.
Optics: image projectors
Relief illusion
353 38, 353 67, 359479, G03B 2128
Patent
active
055087639
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a projector for demonstration and advertising purposes with a system of convex lenses on the side of the object and a system of convex lenses on the side of the image.
Such projectors are normally used for the projection of two-dimensional illustrations on film, foil, and paper, upon a screen or a ground-glass disk. The reproductions are also two-dimensional and make a rather flat and poor impression unless one works with certain tricks of the trade, such as, for example, multi-colored images that are projected on top of each other, and corresponding glasses. The same applies to illustrations using video equipment on screens.
In addition, holograms are occasionally used for advertising purposes; these holograms reproduce a three-dimensional image of an object. Holograms, however, require a complicated recording technique that only shows the three-dimensional image of the object used during the recording in a single position.
In contrast, the invention is based on the task of creating a projector of the kind mentioned initially which, in addition to its ability to reproduce two-dimensional images, will in particular also be able to provide the plastic reproduction of physical objects and which, using very simple means, will generate a three-dimensional image for the observer that shows a three-dimensional object that is "positioned in space."
The problem is solved by the invention in that the baseboard is made to hold a three-dimensional object, with the system of convex lenses on the side of the image including a Fresnel lens, while the length of the beam path, measured along the optical axis between the system of convex lenses on the side of the object and the Fresnel lens, is essentially equal to the sum of their focal distances, the diameter of the lenses being greater than the extent of the object to be reproduced, as measured transversely with respect to the main axis of the system of convex lenses on the side of the object, and whose interval from the system of convex lenses on the side of the object is so small that the object is reproduced at least partly behind the Fresnel lens as a three-dimensional aerial view.
Using the equipment proposed here, it is possible to generate a three-dimensional image for an observer who essentially looks along the optical axis toward the Fresnel lens from behind; this three-dimensional image reproduces an object arranged in front of the system of convex lenses on the side of the object. By properly selecting the focal distances of this system of convex lenses and of the Fresnel lens, an enlarged or reduced image of the object can be generated, as desired; by means of the interval between the object and the system of convex lenses, one can determine whether the image is completely behind the Fresnel lens as far as the observer is concerned or whether, because of the three-dimensional depth of the object, it appears partly in front and partly behind the Fresnel lens.
By convex lens system one means here not only individual lenses, but also systems consisting of several lenses, even if they contain one or several dispersion lenses, so long the lens system on the whole has focusing properties and thus a positive focal distance on the side of the image.
The system of convex lenses on the side of the object and the Fresnel lens in this case form an afocal or almost afocal system because their mutually facing focal points coincide, or are only up to about 10% of the sum of their focal distances away from each other. In that way one can make certain that the object to be reproduced will be shown three-dimensionally over all of the depth planes of the object area, that is to say, independently of the width of the object, with essentially the same reproduction scale.
An impressive three-dimensional effect of the image thus generated can also be traced back to the fact that, in the proposed projector, the lenses are greater than the transversal dimension of the object to be reproduced. In this way, the optical system "sees" not only the surfaces of t
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patent: 4078854 (1978-03-01), Yano
patent: 4386833 (1983-06-01), Hirose
patent: 5293188 (1994-03-01), Yoshida et al.
Dowling William C.
SW Stanzwerk Glarus AG
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