Optics: image projectors – Miscellaneous
Patent
1996-03-25
1999-02-16
Dowling, William
Optics: image projectors
Miscellaneous
353 62, G03B 2114
Patent
active
058712674
DESCRIPTION:
BRIEF SUMMARY
This is a United States national application corresponding to international application PCT/EP94/01888, filed Jun. 9, 1994, which in turn is an international application corresponding to German application No. P43 19 680.2, filed Jun. 14, 1993, the benefit of the filing date of which is hereby claimed under U.S.C. .sctn.120.
The invention pertains to a process and a device for producing two- or three-dimensional images in gaseous media, in particular in earth atmosphere.
In the prior art, so-called "floating" images are produced in the sky at night in so-called "laser shows" by means of lasers which work with visible light above the heads of the audience. These images require a projection surface, however, which in most cases is a thin gauze which cannot be seen in the dark night sky and which is partly translucent. In other cases, fog or smoke is used for constructing the image, whereby the laser light is reflected or scattered onto the fog drops or the smoke particles so that the observers can see an image. If fog or clouds of smoke are required to produce an image, this is firstly an interference in itself and secondly the observer, on account of unavoidable scatter light caused by air humidity or dust, sees the laser beam(s) with which the image is then produced at the interference or focusing site of the laser beams. The observer consequently never has the feeling of a self-luminous image appearing freely.
Accordingly, it is the object of the invention to provide measures with which luminous images can be produced in gas-filled space and especially in the atmosphere without projection surfaces or aids such as fog or smoke having to be used for this.
This object is achieved with a process comprising the features stated in patent claim 1.
Further, advantageous embodiments of the process according to the invention and a device suitable for carrying out this process are cited in the subclaims.
FIG. 1 shows the schematic design of a device according to the invention with two laser-beam deflection systems
FIG. 2 shows the same arrangement in a block diagram.
The invention proceeds from the knowledge that nitrogen and oxygen molecules can be ionized in very large electric fields (field ionization) and that on recombination or recapture of an electron energy is set free which is then delivered from the respective molecule as light radiation (light flash) in the visible spectral range. If such luminous phenomena are caused at predetermined points, for example points of a two-dimensional or three-dimensional matrix, a two- or three-dimensional image can be produced. A light spot which is repeated at approx. 25 Hz appears to the observer to be still. The human eye has a resolution of about 1 arc minute. At a distance of 100 m from the image to be produced, a line can thus be drawn if the light spots produced are spaced at about 3 cm.
According to the invention, the light spots are produced by one or several beams of lasers, which preferably emit outside or at the edge of the visible spectral range, being bundled at the respective intended site at which the light spot is to appear. A suitable device is shown in FIG. 1. Laser beams or beam pulses (1) are produced by one or several lasers (1), whose beam cross-section is initially fanned or defocused in an optical device (3), e.g. by means of a mirror or a lens. The bundle of laser beams falls from the diverging mirror (3) onto a focusing mirror (4) which bundles the received laser light and focuses it at a distance of 10-100 m in a small area in which the field intensity is then so high that the atmospheric gases therein, principally nitrogen and oxygen, are ionized. The ionization occurs directly after the laser pulse on account of the high recombination probability. In the arrangement shown in FIG. 1, for example a CO.sub.2 beam or also a YAG laser is used. Such a laser emits in the infrared spectral range so that the observers cannot see the laser beam but only the effect it causes, i.e. the light flash (9) or the image composed of such light flashes (9).
The d
REFERENCES:
patent: 5450147 (1995-09-01), Dorsey-Palmateer
patent: 5649827 (1997-07-01), Suzaki
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